Like usual, I own nothing, and I am only doing this for fun.
This is set during the events of Episode 4, after Sakura and Misaki's sparring match.

It was dark out, and the members of Berserk were starting to leave the building to rest up for tomorrow. However, Misaki decided to stay behind for a while so he could talk to Rio about Sakura.
Once Misaki discovered Sakura was about to resign, she decided to try and help Sakura reconsider and stay. While Misaki will admit Sakura has a long road ahead of her, she knew Sakura had potential; she's seen it before. And Misaki was not about to let Sakura throw it all away so easily.
And after their sparring session, Misaki felt she may have left a positive impression on the rising star.

One-by-one, the Berserk wrestlers all left, until only Misaki and Rio were left in the gym. And Rio was about to leave until Misaki called for her.
"Rio! I need to talk to you for a bit before you leave."
Rio let out a quiet groan of annoyance and agitation. She was ready to leave. Nevertheless, she knew Misaki was superior to her, and resistance would be futile.
"Yeah, Misaki?" she asked as she turned around and gave the idol-gone-wrestler her undivided attention.
"I need you to promise me one thing before you leave here tonight." Misaki began.
"And that is?" Rio beckoned as she crossed her arms.
"I don't want you to give Sakura a hard time. She's already been through enough crap as it is." Misaki told her. "She already has a ridiculous losing-streak above her head, and I don't want you to make the issue worse. Understand?"

By this point, Rio was already agitated. Her body ached, her shoulders hurt, and she was just tired and wanted to rest. She wanted to go home and take a nice, warm, and relaxing bath to soothe her muscles and relax. But when Misaki stopped her from doing that JUST to tell her to leave Sakura alone, Rio became beyond annoyed and mad.

"Oh, you have got to be freaking kidding me." Rio said in utter annoyance.
"No, I'm not." Misaki told her, dead serious. "I'm taking her on as my pupil, as I want to help her improve and reach her true potential."
Rio "pfft'd" at Misaki with a smirk. "Sakura actually having potential. Ha! That's a good one." she said with a laugh. One that died pretty quick when she saw Misaki wasn't laughing.
And not only did Misaki not find it funny, but she walked up to the white-haired wrestler and punched her hard across her temple, dropping Rio with a loud yelp, leaving her on the ground clutching her head in pain and groaning.

"Not so funny now, huh?" Misaki asked with a glare as she crossed her arms. Rio glared at her as she got up.
"If you ask me, you should cut her out and tell her to beat it." Rio spat.
"Well, if you ever take my title from me, then you can call the shots." Misaki told her. "But until then, shut your mouth."
Rio rolled her eyes and growled in annoyance. "Oh for the love of-" she groaned. "Misaki, do me a favor… and GET REAL!" she suddenly shouted. "SAKURA IS A LOST CAUSE! SHE'LL NEVER BE ANYTHING MORE THAN SOME STUPID, AIR-HEADED, POP IDOL FOOL!"

To say that Misaki was mad would be putting it lightly; she was becoming straight-up infuriated.

"PEOPLE LIKE HER ARE A DISGRACE TO WRESTLING, AND IF SHE HAS ANY RESPECT FOR WHO WE ARE, AND WE DO, THEN SHE SHOULD LEAVE, AND NEVER RE-!" Rio added, but was cut off when Misaki kicked her hard across the same temple she punched earlier, dropping Rio again and making her yell out in pain much louder than the last time.

Both knew that was going to leave a nasty bruise the next day.

Rio glared daggers at Misaki and growled darkly at her as well. She then tried to stand back up, but Misaki held her down by placing one knee on her stomach, and placing one hand on her throat.
"Now you listen to me, you cocky, arrogant, albino-headed fool." Misaki began darkly. "I don't EVER want to hear you say that EVER AGAIN, you got that?!"
Rio actually look genuinely scared of Misaki at the moment; she has seen, time and time again, what Misaki is like when she gets mad. Despite rarely showing it, she has a temper that could make even Digger shake in her boots.
"Regardless of your feelings, I WILL take Sakura under my wing, and I WILL help her get better. As for you, you will remember YOUR place." Misaki added.

With a long sigh, Rio nodded her head. But she still had one question for the Berserk ace.

"Let me ask you something; why are you showing her pity?"

Misaki was silent for a while; not because she didn't know the answer, because she DID know. She just wasn't expecting to be hit with that question.

"I just… see a lot of my former self in her." Misaki finally answered. "And I'm telling ya, it's actually kind of scary." she added with a laugh.

Now it was Rio's turn to go silent. A blank expression was plastered on her face, meaning she had no idea what Misaki was talking about. Misaki took note and decided to fill in the blanks.

"Ok, let me explain. When I first started out, I was an absolute joke of a wrestler. I joined in out of sheer impulse, and because I wanted to avenge Juri." Misaki explained.
"Sanada? How did you know her?" Rio asked, her eyebrow raised in confusion and curiosity.
"...We used to be pop idol singers together." Misaki answered.
Rio's eyes became as wide as saucers when she heard that.
"Anyways, I was doing really terrible, and-"

"WHOA WHOA WHOA WHOA… WHOA!" Rio interrupted. "You used to be a pop idol?!"
"Yes. I didn't tell anyone because I didn't want them to make a big fuss about it." Misaki told her.
"How many others know of this?" Rio asked.
"Not very many." Misaki answered. "Jackal and Kanae know, and Juri, of course. But other than that, none of Berserk know. And I intend to keep it that way until I decide otherwise."

Rio couldn't believe it. Misaki, the ace of Berserk, used to be a pop idol, just like Sakura. Perhaps there is hope for Sakura, she wondered.

"Now, getting back on topic." Misaki began. "I was doing really terrible, and I was on the verge of quitting. However, Jackal must have found out somehow, because she came up to me on the day I was about to quit, she invited me to come spar with her. But what I thought was just simple sparring, Jackal also saw it as trying to help m to understand that wrestling was tough, and that I had to be tougher."
"And I see it worked out well for you, huh?" Rio asked.
"Heh. Yeah it did." Misaki replied. "Anyways, thanks to the sparring session, I learned to toughen up and fight through the pain. I decided I was never going to give up another match, but rather keep fighting until I can't fight anymore, then repeat the process in the next matches to come. And thanks to Jackal, I rose up to become a champion, and I became the ace of Berserk."

"...Wow… I had no idea it was like that." Rio said in amazement.
"Well, now you do." Misaki said. "So you see? It CAN be done, because it HAS been done. Sakura could grow to be one of the greatest wrestlers, not just of Berserk, but in the world. And that's why I can't let her leave so easily. Besides, I heard from our coach that, if she gave up on a lost cause, then a certain silver-haired wrestler wouldn't be here today." she added, a smirk forming on her lips when she said that last sentence. "Sound like someone you know?" she asked teasingly.
Rio's face went red. "*sigh* Ok… I see your point..." she said. "I gotta say; you have more patience than I do. She never would have made it as MY pupil."
"Plus, if I let her leave, she wouldn't have anything to go back to." Misaki pointed out. "I couldn't let her leave like that, because I know the feeling all too well."

Now Rio was starting to understand; Sakura is just a younger version of Misaki. Both have been pop idols, and both went through hardships, with Sakura still going through them.
And while one part of Rio wants Sakura gone, since she feels their rematch will go the same way their first fight did, another part wanted Sakura to stay, as she wanted to see just how good the idol-turned-wrestler would do. It was a mixed bag for Rio.

"Now, there's just one last piece of business to discuss." Misaki said. Rio internally sighed in relief, knowing she could go home soon. "When I called Sakura to spar with me, I saw she was about to turn THIS in." she added as she reached into her pocket and pulled out a folded-up piece of paper. Rio was confused at first, but her eyes widened in shock when Misaki unfolded it, revealing that it was a letter of resignation. Or, more specifically, SAKURA'S letter of resignation.
"I don't know why I'm surprised; the only thing she's good at is giving up." Rio stated, earning her a swift slap to the face. Rio let out a loud yell of pain; her cheek stung from the slap, and she was certain there would be a red mark on her cheek as well.
"Not. One. More. Word. About her giving up." Misaki said angrily.

Rio let out a long sigh. Then, somewhere in the back of her mind, she decided to start a little wager, with the letter as a major part of the deal.
"...One more chace… that's it; one more chance, and if she gives up, she's gone." Rio said.
"Very well… what do you have in mind?" Misaki asked, taking the bet as she crossed her arms.
"Kurea told me that Sakura is her next opponent." Rio explained. "So, if Sakura doesn't give up, not only will I take the letter off your hands, but I'll PERSONALLY give her the letter to destroy, should she ever win a match."
"And if she gives up?" Misaki asked.
"Then YOU will make sure she turns the letter in herself." Rio answered.

Misaki knew she was putting Sakura's career on the line here. Still, it was nice that Rio was giving Sakura another chance. With a long sigh, she spoke up.
"Fine. Deal." Misaki said as she shook Rio's hand.

Now that business between the two wrestlers was over, Misaki allowed Rio to leave the gym, go home, and take that bath she wanted.

But Misaki still stayed behind, thinking about the potential crap she just put Sakura in. Sakura's career, both in the ring and as an idol, are now in jeopardy. But Misaki had to have faith in the young star. That, and she had to hope and pray their sparring session left a good impression on the newcomer.

And thankfully, when Sakura faced off against Kurea, Misaki was right; Sakura was finally going to take pro wrestling seriously.

*And I'm done with this story.
Have you guys noticed I've been giving this series quite a bit of love? I just can't help it; there are quite a few ideas I can use for this series, but mainly stories that take place after or during an episode. And in this case, Episode 4.
Now, the thing about Juri. On the last episode (or second-to-last), Jackal pointed out the similarity Sakura and Elena had to Misaki and Juri. That makes me wonder if Misaki and Juri were originally part of an idol group, similar to Sakura and Elena. We don't know, and we may never know.
Anyways, expect more to come from me. And as usual, I'm Foxboy614, and I bid y'all sayonara.
God bless, and be safe!