LOL wtf Marisa is sad or happy?

Probably happy; I have a feeling it'd probably be a more definite frown otherwise.

Also, since Alice is ambiguiously the daughter/creation of Shinki in the PC-98 continuity, I'm getting some "oh, hey, Alice, I fucked your mom" vibes from this.

Hmmm...
Maybe Shinki [insert a verb] Marisa and Marisa feel too much shame to marry Alice.
LOL

Maybe Marisa sneaks in to have a surprise romp in bed with Alice. She has her way, and when the lights turn on she realizes it is not Alice, and as any comedy goes Alice comes in right after.
If so it can go a few ways by common laws of hentai
1. Alice is mad at Marisa for defiling her mother(doubt that one)
2. Alice is angry at Shinki for going ahead with Marisa
3. Alice thrown into utter shock and disbelief followed quickly by unguided anger

Marisa genuinely seems to be freaking out.

Shinki didn't seem to mind the surprise sex.

Trucidation said:
Shinki didn't seem to mind the surprise sex.

I doubt it was really surprising