Doujin games?

[Shirodramon]

And those games are out only in Japan?

Yes, they are, but you can still buy them, but it may be expensive with having it shipped and stuff.

I honestly didn't buy any of them, they were downloaded. You could probably find downloads for them somewhere. I just used a P2P program to get one of them.

They're kind of old, but Melty Blood is still popular out there.

Note: They're obviously in japanese only, too. The only game that may necessarily need you to know japanese is Melty Blood as it has storylines (the game is the sequel to the Tsukihime anime).