[tenshi no hane]

^ That’s also a nice interpretation! And yeah, I was like “is this some phrase I don’t know about?” until I saw Japanese users also wondering what the hell she means

Originally Posted by tokyoxjapanxfan

My Japanese friend said that koinobori could also refer to having a big mouth but being empty inside, like the physical flags, so it could be a sarcastic dig at boys/men in that way as well. But I think it’s double meaning in that way. Boys/men are represented by koinobori, but coincidentally also talk big but don’t have much to back it up with. (But generally speaking, most of the Japanese TA aren’t sure of this line either haha.)

Reference pic

Spoiler:

I had never heard koinobori having this meaning, so it’s interesting haha.

Yeah, thats also a very interesting interpretation and matches with “you’re all talk, no substance” lyrics.