survivorevil said: some hentai games also has an anime version duh... this is one of them
What's confusing you is that School Days is an animated game. This is not from the anime that aired on TV, it's part of the game animation.
What's going on in the background is that Makoto and Hikari are actually secretly watching Kotonoha and Taisuke have sex which ends up with Makoto and Hikari having sex themselves.
akaanime said: Wait, is she doing with another guy? That is not the main guy...nice boat ending for her?
See Spoiler tag below, but be warned. This is my opinion. The is Makoto's Friend raping her while he was dancing with the other girl. The MAIN reason I say she had every reason to kill him and her by multi-stab to the nutsack/ hammer to the face/alcohol with razorblades in between the toes/ acid enema.