I need help.. what's happened to him?

I have an otaku friend,and we have our group of otaku.. and it used to be so much fun. But senpai changed, he used to be so lively and nice, and now he's been really horrible, and he ignores me when I try to talk to him. Even worse, he had been really snappish and cold. When I attempted to talk with him again,he had just got into an argument with my big sis... he frigging insulted her and I refuse to let, even a friend get away with such a thing. So now we're pissed at each other and I want to throttle him. (I apologize for sounding really shallow and ranting. If this bothers you, you can ignore it. Sorry again.)

If he's also arguing with your sister, and possibly with others, then he's probably having personal issues, and that it might not be directly related to you. I personally like to get through to people and find out what's wrong, but maybe he just needs a little time to himself. I wouldn't pressure him too much, it might just push him away further, even if you're trying to help or find out what's going on. I'm sorry I don't have any real advice for you. But if I were you i'd give him a little bit of time.

I hate people who do that. Like if you have a problem, friggin just say hey I have a personal issue, I'm not going to be very sociable and I don't wanna talk about it and I'd be like awesome, hope you work it out. I'd probably say fuck it, he'll talk to me when he wants to and just leave him alone if I was in your situation.

Honestly, sounds like he needs time to himself. If he cares enough, he'll come back to you guys on his own terms as long as you show that you're willing to talk to him no matter what happens. Just don't change your attitude to him too much and eventually, he'll go back to normal in all likelihood, assuming what happened isn't life-changing.

sempai huh? so Kawaii! o_o *cough* Well there definitely is a problem. a big one. hmm. the best way is to analize it correctly. since this was posted 2 weeks ago idk if the status changed or not but when most guys get pissed they don't spread it to other friends. most people act aggressively towards those that caused the aggression. (sometimes not all the time) But maybe he was sending signals and you rejected him or maybe said something bad? kinda hard to say with such a short vague paragraph. give him time. he will explain himself soon.