Shouta Aizawa

He becomes really distant, he doesn't cuddle, he doesn't kiss and he seems awkward and mad around you. It'll take some talking to, but you'll finally find out that he's jealous of another person. Him admitting that just makes you show him tons of affection.

Nemuri Kayama

She'll get into fights with you. She'll become mad over small things and sometimes try to end the fights with sex. But you decline until she tells you what's actually wrong.

Tsuyu Asui

She also becomes distant. Her smiles at you will often turn into frowns and she'll mope about with round shoulders. Sometimes you'll find her crying or on the verge of tears before you find out what's wrong.

Uraraka Ochako

She becomes hella protective and out-there. She'll force herself to kiss you in public, put her hand on your lower hips, lay her head on your chest and just do things she's never really comfortable with. Sometimes she'll either do something that pushes herself too far or pushes you too far. After that, you'll both talk it out.

Denki Kaminari

He gets pretty sad and hugs you like every time it's going to be your last hug with him. He'll murmur that he loves you, instead of shouting it proudly.

Eijiro Kirishima

He gets winey and needy. He constantly asks; "Do you love me?" Which you will always reply with an "Of course I do." Eventually, you'll ask what's going on with him and he'll confess like a guilty dog.

Shoto Todoroki

He'll become distant. It's like he's preparing to hear you say 'I've found someone else.' Whenever you ask for hugs he'll hesitate, or flat out decline. That's a big worry, Todoroki never turns down your hugs!

Katsuki Bakugou

Boom Boom. He'll try to talk to you about it but end up getting flustered and telling you're stupid and he's going to kill whoever he's jealous of. If it wasn't directed at Deku, then you'd figure out something was wrong and ask him about it.

Izuku Midorya

He a sad boy. He already thinks you're too good for him so when he's jealous he becomes determined but also feels sad late at night. "I'll work harder! I'll- I'll be the man you want!" He'll get all teary-eyed and inspirational. You'll roll your eyes and put your hand on his head. "You're already the man I want." You would say. Then he'll cry with his head buried in your chest.

Momo Yaoyorozu

She'll become somewhat dominant and keep you close at all times. She'll squeeze your hand, grab you by your waist, etc. She's just more touchy-feely and protective. You don't really mind it, so you won't say much.

Hitoshi Shinso

All the time you two spend together he is always smiling, but really he's just sad. He tries to enjoy every moment with you, but it really just feels like your faking it to make him happy. You'll see that he's looking more down than usual. He'll ask why you love him, and you'll tell him why. He'll get happier after some reassurance.

Mirio Togata

He gets frustrated. He will usually go train to get his anger out on something but he'll still be outward in telling you why he got so angry.

Nejire Hado
She's as pouty as ever. She tugs onto you more and basically feels like you're ignoring her. You'll need to give her some words of encouragement before she goes back to normal. 

Tamaki Amajiki

He begins to tell you how much he loves you, like he'll never be able to tell you again. "I l-love you m-more than a-anyone." He'd stutter. If you feel he's becoming too sappy, you'll hold him in your arms and return the favor. "I love you more than anything." Your words would soothe him, and he wouldn't feel so sad anymore.

Camie Utsushimi

She stops sending you vines on Instagram. She gets very needy when you two go on dates and tries to seduce you a little bit too much.

Mt lady

She makes excuses not to hang out with you and tries to get on TV more, hoping you'll see her. When she gets home she'll say; "Did you see me capture that villain?" You'll say yes followed with a compliment and she'll be happy from then on.

Endeavor 

Seriously? He's abusive, he'll beat you no matter what.

Dabi

He'd most likely kill whoever he's jealous of. Once you found out, you'd just tease him about it. "Is someone jealous?" He'd 'tsk' you and look away. "Awe, you're such a sour puss." You'll kiss his scars and tell him you wouldn't look at anyone else.

Himiko Toga

Killing spree! She'll murder whoever she's jealous of and then become them, she'll flirt with you in their body and once you've rejected them she'll turn back and hug you. "Yay! I knew you only loved me!"