Dragon Girl

This is a fantasy world.
The protagonist and the heroine are adventuring partners.
The heroine wants to experience things like laughing and crying together when they're out on an adventure, and yet the protagonist's attitude towards her has gone cold lately! Furious, she asks him for the reason and he says it was because she was making him horny!
What does "horny" mean...?

The story of their flirting begins from here.

(Source: DLsite, translated)

Note: Released at Comiket 96.