This visual novel contains sexual scenes involving a Japanese sexual practice called "wakame sake".

Wakame sake it's a body food sexual act that consist of puring sake between woman thighs of a naked woman, while she keeps thighs shut together in a way that they form a container. Then another person drinks from it.

Wakame Sake is a Japanese sexual play that used to be played between Geisha/Yuujo prostitutes in Yuukaku prostitution mainly up until 1956. The reason why it's called "Seaweed" is because the pubic hair in sake looks like wakame seaweed in the sea.

Even though it's not usual, it can be performed with other kinds of alcoholic drinks, which can be poured in other parts of a naked body like tits for example.

Thighs Wakame Sake: NSFW Example 1, NSFW Example 2
Tits Wakame Sake: NSFW Example