Chapter one:
"Ugh! Good going leader." Raph groans glaring at Leo after they got in trouble again.
Because Leo just had to tell their father where they actually were.
The three stalk off in anger and disappointment.
"Wait! Guys I didn't..." Leo starts only for his shoulders to sag as they don't even glance back. He turns away sneaking into the tunnels and sighs with his head down. His eyes momentarily closed as he feels guilty and hurt. "I'm actually a part of this family... Right?"
"Do you really think they actually want you in their family?" A voice makes Leo's head jolt up in surprise, and his now open eyes glance around.
"Who said that?" Leo questions then turns to look ahead as a figure fades into view.
"I did." The figure looks like a turtle mutant that is made of shadows with dark blue outlines. It also has solid blue eyes, and outlines of sharp teeth with the inside of its mouth being blue.
"W-Who are you?" Leo questions as he gets a bad feeling just looking at this thing.
"I am what is called The Shadow. Your Shadow in this case." The creature greets Leo with a slight chuckle. "I've been watching you and I know all that you've done."
"What I've done?" Leo isn't fully sure what to make of this situation.
"Why yes. How you make your brothers dread coming home. Because they know you'll ruin a good night out by telling on them. How they dislike you so much because you can't properly have any fun. Oh yes. I have seen the looks on their faces. You're just a disappointment to them. I bet they wouldn't even notice if you lagged behind when returning home."
"Of course they would!" Leo tries to defend that only for the being to chuckle.
"Then why not put it to the test? See who is right. Not that it matters to me. I think I'll hang around for a bit. You won't be able to get rid of me very easily." Shadow almost sounds taunting as it speaks and Leo decides to test its theory. He'll prove it wrong.
"Fine. Next time you'll see that they'll notice. If I'm right you leave. If I'm wrong you can stay."
"Making your own bargains I see. Well we shall see about that." Shadow is smirking the whole time. "Oh. And let's keep me as a secret. Unless you'd like to make them think you're crazy. I can make myself invisible so it's just seem like you've gone crazy. Taking to thin air."
"Okay?" Leo heads back to the lair and heads to bed.
"How much extra did you tell?" Mikey glances to Leo who is about to shift to lay down.
"Nothing. I wandered a little before coming to bed. Didn't go far or even on the surface." Leo shrugs and settles in for the night. He is sure that there is a way to get them to the surface again. He'll find it if there is even a way to do so. He might have to take away Splinters stash of something they pick up anyways.
The next morning...
Leo wakes up before everyone else and he peeks into the kitchen area. "Okay." He whispers. "Just gotta grab something." He spots the cheese and takes it hiding it under his bed. He silently tells himself he'll put it back later. He pretends to still be asleep and waits.
"No!" A shout jolts them awake before Splinter hurries in. "Did you boys forget the cheese?!"
"I thought we got some." Raph mumbles tiredly.
"Wasn't that Mikey's job?" Donnie groans.
"I did grab it!" Mikey insists and Splinter sighs.
"Never mind that. You four can go out to get cheese. But come back immediately!" Splinter heads off after that.
"Ugh. What a morning." Raph stretches after getting up.
"Let's go." Leo gets up trying to ignore Shadows chuckle as if about to proved right. "The sooner we get this cleared up the sooner we can do what we want."
The others grumble but do get up heading out with Leo.
"The north market should be still closed at this hour. We can grab some there." Donnie mentions so they all hurry that way.
They arrive and Mikey takes charge of covering the security camera aimed where needed.
"Okay Raph. Go." Leo tells Raph who jumps down grabbing an armful of cheese then using a wall to jump back up.
Donnie and Leo pulling him back up into the ceiling.
"Good. Now let's get home." Leo suggests. "So we can finally have some breakfast."
"I guess. Wish we could have checked out human things." Raph mentions with a shrug.
"There isn't really anything going on today at least not for awhile." Donnie glances up from his phone. "Nothing we could check out anyways."
"Fine!" Raph groans and they make their way back.
Leo watches as Raph and Mikey flank Donnie asking to see what events are happening. He knows that this is his chance as they all walk home. He slows his pace falling further and further behind. He doesn't get noticed and slows to a stop watching his brothers head off without him.
"What did I tell you?" Shadow questions coming to stand next to Leo. "They don't care about you."
Leo lowers his head. He's such an outsider in his own family. He turns as a hand comes onto his shoulder. His eyes meet what is considered to be Shadow's eyes.
"You don't belong there. You're not family. And you're certainly no leader. It's going to be a great relief to have you gone from their lives."
"What do you mean by that?" Leo questions unsure where this is going.
"I can help you. I can give you a purpose in life. Help you get what you've been wanting for so long."
"To be the best leader for my family?" Leo blinks at Shadow that shakes its head.
"No. That is just something you thought of to try to make yourself actually useful to them." Shadow informs him. "What you truly want is a way to fit in. A way to belong somewhere. And I can help you with that. For one small fee."
"What's this fee?" Leo questions and Shadow chuckles with a smirk.
"My dear everything has a price." Shadow lets him know staring so deep into Leo's eyes; Leo could swear the other can see his soul. "And my price is that you agree to become my host."
"What?!" Leo isn't so sure about this being a small fee.
"You don't need to worry. I won't harm them. You have my word. You'll just become a better brother. You'll belong with them finally. I only want to help you. Just give me your body, you'll still reside in it with me, and I'll make your life better." Shadow offers its hand to Leo who glances to it. "What do you say?"
Leo glances away with hesitance. "Hold on a minute." His eyes glance back and forth as he thinks over what is going on.
Meanwhile...
Raph opens the manhole cover. "Alright." He turns and blinks in surprise then confusion. His reaction causing Mikey and Donnie to blink confused. "When did we lose Leo?!"
The other two look around realizing that Leo isn't with them.
"Ugh. Let's go find where he went." Raph stomps back the way that they had come. He hears the other two following though not stomping.
They see Leo up ahead about halfway.
Leo is looking away and is looking at something that isn't there. "I hardly know you. I'm not so sure about trusting you with that." He mentions shaking his head.
"Who are you talking to?" Raph questions making Leo jump then spin around to them in surprise.
Leo glances back before turning back to the confused three. "No one I guess. I thought I saw something and heard something. But they're not there anymore."
"Are you losing your mind?" Raph questions gently flicking Leo's forehead.
"Well maybe a human was trying to lead him away?" Donnie suggests. "But left when we came?"
"I think that's what happened." Leo nods his head to Donnie. "But of course I wasn't going to follow them."
The three look glad that it is settled.
"Well then let's get going. Pops is expecting us back. And I am not going to get in trouble because of you." Raph turns away pausing as Leo speaks up.
"If we do I'll take the blame. It was my fault." Leo promises and together they all head home. He'll grab the cheese from under his bed when no one will notice.
Though only Leo can see it Shadow follows after them.
That night...
Leo is laying on his bed awake after having snuck the cheese back into place. He's just glad that they didn't get in trouble as Splinter was just happy about the cheese. He glances up as Shadow stands over him.
"So. About my offer. I can give you what you want. Fix all that you've done to make your brothers dislike you. No one actually cares about you. They left you behind. Only coming back so they wouldn't get in trouble." Shadow leans close to Leo's face. "I am offering you a chance of a lifetime. Take it. Or you'll regret not taking it."
Leo rolls over trying to ignore Shadow.
"You can't just ignore me. I will follow you until you let me help you. It is my only purpose in life." Shadow sits by Leo's bed with its back to it. "You'll come around. I know you will. You lied to your brothers. You've already started to let me in." It doesn't miss Leo tensing at this. It chuckles softly. "Oh Leo. You can be such an idiot sometimes. Though that's why I was called to help you. Help you fix your life."
"Let me sleep." Leo mumbles dismissively.
Shadow smirks. "Alright. Have a good rest. Leo." It waits for Leo to fall asleep preparing some magic.
Leo closes his eyes and it takes a bit before he's able to fall asleep. He finds himself standing facing his brothers who look angry and disappointed.
"We shouldn't be taking you with us anymore." Raph growls out glaring daggers at Leo who shrinks back.
"At this rate we won't even be allowed on the surface." Donnie looks away in disappointment.
"Come on! It's like you don't even know how to be cool dude." Mikey sighs shaking his head with his eyes closed.
"Guys." Leo tries to plead only for them to turn away and leave him alone. He reaches for them though when they notice they run off. He falls to his knees finding tears coming to his eyes. He suddenly jolts awake with a gasp. He has to even out his breathing then glances to his brothers. He lets out a breath seeing them asleep. He also happens to notice Shadow sitting, on the floor at the end of Leo's bed, just watching the rooms entryway. He brushes it off and tries to go back to sleep without success.