The group made it some distance away before they stopped to catch their breath. "Okay—Oh for God's sake, what is happening? Why are Servants other than ours here?" said Olga in annoyed panic.
"I see… A Holy Grail War? A Holy Grail War was going on in that town! Normally, it would be a battle royale amongst the Seven Servants summoned in Fuyuki. But something's gone terribly wrong. I'm not surprised there's a Servant without a Master. It's natural for Servants to target other Servants," explained Dr. Roman.
"Then as long as Lily and I are here, we'll be targeted by other Servants?" said Mash in a bit of a self-loathing tone.
"But Mash has nothing to do with the Grail! That's just a wandering phantom gone mad!" said Olga.
"Is this what always happens to Servants without Masters?" asked Issei.
"It's not always the case, but it's not uncommon either," said Dr. Roman.
Before the conversation could continue, someone had suddenly appeared, putting them on alert. "—I found it. New prey. The Grail shall be mine!"
"Servant's signal confirmed, it's an Assassin-class Servant!" warned Dr. Roman.
Issei was preparing to fight when he was stopped by Lily. "Master, please stay back. The monsters were one thing, but Servants are another. If something were to happen to you, then I would disappear as well. Leave this to me and Mash-san and save your power."
"I can fight! Senpai, please give me your orders!" said Mash with determination, standing beside Lily.
Issei wanted to object, but he felt like Lily wanted to earnestly protect him. Issei also could tell that these Servants were no joke. He felt like they were as dangerous as Cao Cao or the others from the Hero Faction. He looked at Ritsuka, who met his gaze. They nodded and Issei spoke. "Ok Lily. I'll leave it to you two. But I'll jump in if things get dangerous."
Lily nodded and the two readied for combat. Mash also readied herself, with Ritsuka giving her order. "Let's make it through this Mashu!"
"—Okay. I'll bring you victory, Master!" Mash said with resolve.
The Assassin charged in, aiming for Mash, only to be met by Lily who cut him off and swung her blade. The Assassin brought out a knife and clashed with Lily's blade. The two moved quickly as they clashed around the battlefield. Lily had more power behind her, but Assassin had more speed, maneuvering around Lily more easily. Assassin tried to stab Lily from behind, but Mash rushed in, bashing Assassin away. He let out an annoyed "Tch!" as he changed his target to Mash, but Lily immediately backed her up. The two took a literal sword and shield approach to battle as Lily went on offense while Mash did her best to cover any attacks Lily couldn't parry. Issei was stressed, wanting to jump in and help but forced himself to stay put and trust Lily and Mash. Ritsuka looked a bit tense as well but watched the battle. The two pushed the Assassin back and the three seemed to be on a stalemate. Lily looked fine while Mash was breathing heavily, clearly not used to fighting such a strong opponent. "All right—How about that!" exclaimed Mash as she tried to strike Assassin again.
Assassin was pushed back but looked more annoyed than anything. "—This is a waste of time. I could have handled this on my own," he said ominously.
"...What does that mean?" asked Ritsuka warily.
Issei seemed to pick up on what he meant as his eyes went wide. "Mashu, Lily, fall back!" he yelled.
"Ritsuka, Issei, they've caught up! There's one more, that's their main force!" warned Roman over the comms.
Another Shadow Servant appeared next to Assassin. "No way… We're having a hard time with one already, and now there's one more here?" said Olga, growing fear appearing on her face.
"Let's finish this, Lancer. I don't know what kind of Heroic Spirit that is, but I will have her head. —Ha. Hahahahahahahahahaha!" said Assassin, as if proclaiming victory.
"Director, Mash, Issei, hang in there! You got to keep moving!" Roman tried to encourage them to make a break for it.
"Fou! Fou!" Fou was trying to keep their spirits up too.
"—Ha. Hahahahahahahahahaha!" the new Servant laughed maniacally.
At this point Issei decided to step in. Lily saw this and gestured for him to stop, but Issei wasn't having it. "Lily, we can't afford to hold back now. I'm joining in so we can deal with this quickly."
"...Very well, Master," she said with some reluctance.
"You two deal with Assassin, I'll handle the new guy."
Lily looked at Issei in shock. "Master! That's too reckless! I will–"
"Mashu needs you more than me. I'll be fine. Trust me," said Issei reassuringly as he got ready to fight.
"Senpai!" Mash called out to Ritsuka, asking what to do.
"We have no choice but to fight! Follow Issei's lead," she said.
"...Understood, there's no other option!" said Mash resolutely.
"Ha! Futile! Fight, then you die. Run, and you still die. The demise of the futile, oh so miserable," said Assassin mockingly.
"Go ahead and struggle. Miserable people are ever so entertaining," said the new enemy.
"F-Fight? Are you serious? We don't stand a chance against something like that, right?" said Olga panicking.
"...Even so, we must fight. We will find a way to get out of this alive!" said Mash, now more determined.
"Damn right! Let's go, Mashu, Lily!" said Issei
"Ha— You've just killed yourself, fools!" said Assassin.
"I thought you were just some kids, but it looks like you've got some fight in you. Then I can't leave you like this," said a mysterious voice.
Suddenly the Shadow Servants exploded from an unexpected attack. "Ugh! Who are you?" asked Assassin, irritated.
"What do you mean? Can't you tell? Don't tell me the mud got in your eyes too?" said a man who suddenly appeared next to Mash. The group was surprised as the Mystery Man addressed them. "Don't worry, I'm here to help. I'll help the little lady here. You can go help your Master. We'll talk after," he said. Lily gave him a wary look but nodded as she moved to Issei's side.
Issei and Lily charged the new enemy. The Lancer had several weapons at his disposal as he attacked the pair. Lily parried his attacks with her sword while Issei did his best to dodge them. One attack managed to land and push Issei back. He was worried at first but saw that his armor only cracked. It still hurt like hell though. Lily started attacking Lancer more fiercely, getting his attention. Issei decided to fly up above, before diving down, preparing to hammer arm the enemy. Lily was pushed back by Lancer and he prepared to finish her, until Issei came down on him, striking him in the head and smashing him into the ground. The force of the attack created a small crater with the Shadow Servant imprinted in it. Issei jumped back next to a now shocked Lily, still eyeing the Lancer to see if he would get back up. "M-Master… How are you so powerful?"
Issei looked at Lily and rubbed the back of his head sheepishly. "I just trained. Granted, I trained in various ways, including having a crazy dragon train me in the mountains for nearly a month," he said in a slightly tired voice, earning a bewildered look from Lily.
Meanwhile, Mash and the Mystery Man were holding off Assassin, with the man firing magic at Assassin as he dodged around. When Assassin tried to get close, Mash would get between them and bash him back. "Enough of this!" yelled Assassin as he moved to go around the back of the two.
The Mystery Man smirked as, without looking back, he extended his hand back and runes appeared in the air. Vines extended from the ground and grabbed Assassin. "Gotcha!" he exclaimed as he gestured his hand to the ground, making the vines smash Assassin into the ground. Assassin was dazed but struggled to break free. That was until Mash came down with her shield and bashed Assassin in the face.
Assassin let out a weak curse. "Ugh— Curse you, Caster, with the Holy Grail, before my eyes—" was all he said before fading away in black mist. The pair looked over at Issei and Lily who were walking towards them. They saw that the other Shadow Servant was also dissolving away.
"Uh, excuse me… Thank you very much, for saving us from danger…" said Mash warily.
"Yeah, that was a close one. We owe ya," said Issei.
"Hey, good work. You guys don't owe me for this, so don't worry about it. You should be more worried about your own bodies. That damn Assassin kept targeting your butts like a pest!" said Caster.
"Oh!" said Mash as she blushed in embarrassment.
"Hey, you look fragile, but you have a pretty nice body! Icing on the cake! I have no idea what class you are, but you're pretty sturdy… Maybe Saber? No, you don't have a sword," said Caster as he seemed to be examining Mash.
For some reason, Issei felt annoyed by their savior's behavior. Olga also showed an uncomfortable expression. "...Hey Ritsuka, Issei, what did you think of that?"
"...He's an ally, maybe?" responded Ritsuka, unsure.
"Without a doubt, he's an old pervert," said Issei.
"For now, let's get some information. He seems to be a decent Heroic Spirit," suggested Dr. Roman.
"Oh, so someone who wants to cut to the chase. What is this? Some means of communication through magecraft?" asked Caster with mild interest.
"Well met, Caster Servant. I don't know which Heroic Spirit you are, but we have nothing but respect and awe for you," said Dr. Roman, in an overly magnanimous way.
"Oh, spare me your remarks. I'm sick of hearing them. State your business, weakling. Isn't that what you're good at?" said Caster, annoyed.
"At least he picked up on that fast," said Olga under her breath. Issei, Ritsuka, and Mash couldn't help but nod in agreement.
"Uh… I-I see. All right then…. Weakling… I got called a weakling from someone I've met for the first time," said Dr. Roman, a bit disheartened. He then went on to explain the current situation to their new ally and why they were here. "...And that's the current situation in Chaldea. Currently, Ritsuka is the acting Master and in the middle of field research. Let me confirm something. You're a Servant from the Holy Grail War that broke out in this city, and the sole survivor?"
"If by that you mean I haven't lost. Our Holy Grail War changed to something else entirely along the way. I don't know how it happened either. The city was engulfed in flames, and the humans vanished. Only the Servants remained. Saber was the first to resume the Holy Grail War. That chap began rampaging like a tiger released from a cage. Archer, Lancer, Rider, Berserker, and Assassin were all defeated by Saber," explained Caster.
"The survival of the Seven servants… That rule of the Holy Grail War was broken here," said Olga. Issei was doing his best to follow along, but he was completely lost. He looked over at Ritsuka and saw that she looked a bit lost too. Mash on the other hand looked like she understood, so he figured he would ask her later. Ophis and Great Red looked like they didn't care about what was going on either and were diligently staying by Ritsuka's side to protect her.
"And in the end you won, Caster… Or rather, you're the Servant who survived," said Mash.
"Yes. Any Servant that was defeated by Saber became like those two, corrupted by the black mud. They, and the monsters that sprung up like maggots, started looking for something together. The troublesome part is that I'm one of the things they're looking for. You see, the Holy Grail War won't end until I'm killed," said Caster.
"You and Saber are the only surviving Servants… Then if you defeat Saber…" Dr. Roman was putting the pieces together.
"Yes, that would probably end the Holy Grail War here. But I don't know whether things would return to normal."
"I see. You helped us, but in the end, it was for your own sake, huh? You want to defeat Saber, but you don't stand a chance doing it alone. That's why you zeroed in on us… Right?" said Olga, understanding Caster's angle now.
"That's right. But it's not a bad deal, is it? At any rate— It looks like we've got company," said Caster, preparing for battle.
More skeletons stalked out from around a building and spotted them. They let out a loud moan as they began heading towards them. "Yikes!" exclaimed Olga in surprise.
"There's no end to these guys. I'm telling you, there's nothing better than having allies!" said Caster in a carefree tone. He was preparing to launch a spell when Issei and Lily dashed forward. Despite his short battle with the Shadow Servant, Issei had a chance to rest when watching the fight earlier. Since the current enemies were more skeletons that couldn't harm him, he decided that ending it quickly was the best solution. Lily, being his Servant, also charged forward and the two completely smashed the group of skeletons. Issei took care of the majority in a few moves, with Lily cutting down any that survived. After a few moments the battle was already over. Caster had a slightly surprised look as he watched the pair return. "Didn't expect that. I knew you could fight since I saw you do it earlier, but to think it was to this extent." He eyed Issei. "Hey kid, what Servant are you? I don't think I've ever seen anyone like you before."
"I'm not a Servant. I came to this dimension by accident and am currently stuck here. I'm helping out Chaldea because they promised to help me get home. But well, I also couldn't leave people in trouble alone, even without their offer to help," explained Issei.
"Not a Servant? Even if you're from some alternate world I didn't think there would be tough guys like you," said Caster in a slightly interested tone.
"Well, I'm strong, but nowhere near the strongest where I'm from. I'm still training to get stronger."
Caster showed a wry smile. "As you should. It's the only way any warrior should live." His words seemed to come from experience as Issei could tell.
Mash cleared her throat to get everyone's attention. "Sigh… Things have settled down at least. True, we can't have a decent conversation like this."
"My bad. If I'd been summoned as a Lancer, I could've finished off Saber with just one strike. Man, Caster is just not for me. I don't like being a Caster in a Holy Grail War like this."
"If you were a Lancer?" asked Ritsuka, confused.
"You can be a different class?" asked Issei, curious.
"It's been known to happen, Senpais. Some Heroic Spirits have the attributes of multiple classes. He is not just a spear-wielder, but a high-level Heroic Spirit with qualifications to be a mage. ...I'm only speculating, but he must be one of the top Servants. The kind that's featured in the magazine Vivian," explained Mash.
"Ahh yes, you said you were the Masters of an organization called Chaldea… I guess that's all I need to know. In general, Servants tend not to get overly involved in problems outside of their own time period. We ultimately only cooperate as weapons. Your goal is to investigate this anomaly. My goal is to put an end to the Holy Grail War. We share mutual interests. So how about we join forces?" offered Caster.
"...That is a rational proposition. But if we do that, who will be your Master?" asked Olga.
"Well that young lady there, of course. The kid is a wild card, and the little girl there doesn't seem to even know what's going on. It doesn't seem like you have the aptitude to be a Master either. I mean you possess high quality magical circuits, yet you don't have the aptitude to be a Master. Is it a curse?"
"Oh, shut up! What do you care? Ritsuka, he's in your hands. Use him wisely," said Olga, irritated. Issei noticed she became upset about the same topic he questioned her on before.
"Then it's settled. The contract is only temporary, but I'm counting on ya. That leaves one last thing, your goal. What you're looking for is probably the Greater Grail."
"Greater Grail? I'm not familiar with that. What is it?" asked Dr. Roman.
"Oh good, so it's not just me who's confused," said Issei.
"This land's true "heart". If there is indeed a "Singularity", it has to be that. But Saber is lingering around the Greater Grail. The remaining Servants she contaminated, too," explained Caster.
"Berserker and Archer are the ones left? What are those two like? Are they strong?" asked Olga.
"Well, Archer can be dealt with if I'm with you. Berserker is the problem. Even Saber had trouble with that monster. But he won't attack unless you get close to him, so ignoring him is one option."
"We understand the situation now. We'll team up with Mr. Caster to obtain the Greater Grail. Mr. Caster, will you show us the way?" asked Dr. Roman.
"Skip the "Mister". I'll take you there. The young lady here will decide when to make our move."
"Much obliged. Then shall we resume the search? I'm counting on you two, Ritsuka, Issei."
"You got it Doc," said Issei.
"Let's find somewhere safe to rest first," suggested Ritsuka. Everyone nodded and they headed out to find shelter.
Here is this months voted for chapter. I think I did an appropriate scenario for Issei's first encounter with Servant type enemies. When thinking about the power scaling for Issei compared to the Servants and Phantasmals, I would put him on a similar level to Shadow Servants and the stronger enemies that aren't Dragons, Spriggans, and some other boss enemies. Of course he could help himself close the gap in power with his Sacred Gear but I'm sure we all know that power alone is insufficient in this world. Other than that, nothing of note besides the usual for this story. The next chapter will be more informative for Issei learning about Servants and the others learning more about him. I look forward to the comments as always.