The protagonist is straight, and he attracts the protagonist gong. There probably won’t be much angst. ₍ᵔ・•・ᵔ₎ Later they become each other’s flag, so to speak (mm-hmm).
Gong: If I can’t have you, I might as well lock you up.
The gong is a bit yandere, and the shou is a bit of a heartthrob.
The mermaid appears from Chapter 6 onward. It’s my personal preference.