Misleading thumbnail, anyone? At first glance I thought Satori was kissing a beheaded Koishi.

Agreed, the head is at a really odd angle, and the arm covering the neck isn't doing any favors. Added to pool.

incest? why? kiss on eyes categorized by incest? well,i should stop doing that to my sister then

I think it has to do with Satori's facial expression and their body positioning. A quick kiss on your sister's forehead is sibling affection. A slow kiss on the eyelid with your eyes closed while tenderly holding her head in both your hands....well, outside of maybe some very specific situations, I'd say that's incest.

I thought she was doing the same thing as Reimu in post #747402