I suppose it's Fate and Nanoha, since Sig. is in there. This doujin is set after the A's series. You will see why I think so in page 2 too...
I notice this doujin has an incredible amount of reference to anime-related stuff. I'll try my best to point them out all, though if I miss out on anything I'd be glad if someone can remind me of it.
Page 2.
Reference: Melty Blood is another doujin fighting game. Note: It's not Melty Blood in the original text, but it's a doujin game I can't translate the name so I just find another random doujin game and replace it.
Page3
Page4
Reference: Fate/stay night. Go to the sub-forum! Note: Arf's master is called Fate, so you can guess how much of a misunderstanding there is going on for Arf...
Page 5
That's all for today.