I've had other ideas about this but really it doesn't make sense that Izuku wouldn't be a gamer of some sort.
I'd like to think that hed use gaming as a kind of venting since he cant fight back in real life he can at least kick ass in COD or something. He uses gaming to create a second persona thats more confident since quirks dont matter in game and no one can see his face or hear his muttering if his mic is off. He becomes a vicious player and his usernames get vaguely violent or villainous.
I like to think that Izuku would vent to what he thinks is some random player and then they start bonding over the unfairness of the current system and heros focus on violent crimes versus domestic situations. Izuku extends this to the police and the media as they exacerbate the issue and really if the heros have the violent criminals then the police should be able to pick up the slack in other areas but no. He exchanges contact info since they seemed to get along. They call each other by their gamer tags or short nicknames as the unspoken rule of not IRL and so they can each keep their personas.
They eventually end up playing alot of games together and set up a semi regular schedule. Izuku finally being able to vent some of his frustrations at the world and analyze it with a cynical person that encourages the negative outlooks starts to become disillusioned with heros. He starts to get more hateful and resentful about the bullying at his school.
The slime villain attacks and All might puts the final nail in the coffin for his hero dream.
He stands on the roof looking at the drop and thinks about all of the negatives in his life like the dream that was just crushed, Katsuki being a terrible human being and his comment about a roof, having no one that would miss him. He gets up to the edge as all the dark thoughts swirl in his head and gets one leg over the railing when his phone goes off. He looks to see its his gaming partner testing him about being late and needing his player 2. This has a mixed effect of joy of someone needing him and him still being an insignificant player 2. Still it pulls him back enough to remember his mom and realize how late it is. He hadn't even written a note so that people would know it was suicide and not a homicide, not that anyone would care or wouldn't be able to figure it out after finding he was quirkless in the records. He starts to walk home and expresses some of these negative thoughts to his friend over text saying something like
"whats it to you, im just a player 2"
He gets an unexpectedly sweet reply from his friend saying something like "how many player 2's do you think I have? Nobody can replace you and if they tried I wouldn't let em" enter other fluff content such as Izuku explaining he was attacked and them getting concerned for him then calling neglect on behalf of the hero for not taking Izuku in for a statement or a med check since he did pass out and should have gotten a med checkup instead of just slapped in the face a few times. Izuku cheers up as they talk and he feels someone cares for him. He looks up to notice hes wandered towards the sound of a hero commotion. Curious he gets closer and sees that its the sludge villain and Katsuki. He mentally curses the hero that dropped him and though a soda bottle was a proper way to transport a villain while trying to get a better view. He sees All might in the crowd and all of the heros short comings for the situation and parts of his own speech echo in his head. Feeling less remorse for Bakugo as he sees the torment hes been putting him through more clearly now he makes his way over to All Might and roasts him by bitterly quoting him "always willing to put themselves on the line to save others huh, dont see these heros doing much of that". He then goes into gamer mindframe and analyzes the situation to show the hero up. He picks up some rocks and moves to the side of the crowd, picks out a good angle and throws a rock right into the villains eye to make him flinch and let go. No one yells at him since he didn't run in and nobody could really tell where the rock came from if they noticed at all. All might knows though and maybe Bakugo notices.
All might doesn't go to him after since he doesn't run in and instead just reminded him of his shame while helping more than him. Izuku gets home to calms down a fretful mother and rethink his outlook on life.
Izuku gets serious about his self defense as the experience was still really traumatic for him and the fact that he came close to dying twice that day gives him some perspective on how vulnerable he is. He starts learning at a dojo and picks some other stuff up on his own. His 'friend' recommends a weapon and maybe learning to hack. He starts standing up for himself at school by taking on more of his other persona outside of video games but the bullying continues in subtle ways of flowers on his desk or tripping him on his way to his desk. Life goes on.
He goes to UA for the exam and gets into the general course since he only got rescue points at the exam and not that many ( he obviously doesn't destroy a zero pointer). He continues talks with his online friend who hes starting to think is trying to get him to join a gang and is doing some sketchy stuff, he almost agrees but wants to stay behind the scenes with his hacking practice for now and act as more of an info broker. He feels this is only mildly illegal while keeping him safe and keeping his friend appeased. He feeds them information both knowingly and unknowingly. Lots of what if scenarios that go into villain planning that he doesn't know about or analysis of the hero students or aid on when would you attack if you were going to attack UA. Inbetween all of this they have been flirting and dropping hints or sappy lines to each other as the socially awkward people they are.
Izuku befriends Shinso and they just click. He pulls him into some of their gamer circles and is somewhere between a love rival and a true best friend. Might make them just queer platonic or a full poly relationship where shiggy just starts collecting abused herolings and rescuing them. (also purposefully left out saying his name on purpose as I want it to be kinda not really mystery for Izuku at least)
