In this game Frisk is going to remain gender neutral.
Viewing post in UT: Kissy Cutie (Complete) comments
"In this game Frisk takes the role of the ambassador to bring peace once
and for all between humans and monsters. The objective of the game is to
convince humans that monsters are not evil. To do that you have to pick
a monster to spend time with the human girl. The game plays like a
dating sim, but everything is purely platonic. This is not a story of
romance, but a story about friendship, struggle, hope and bonds, where
discrimination, prejudice, abuse and manipulation are the villains."
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It says to spent time with the human GIRL.