What’s with the Japanese men in exceedingly tiny bikini bottoms at Kamakura beach

Hello all.

I am a relatively new resident to Japan, in my third year now, and I'm visiting my friends who live near Kamakura so I've been able to spend more time near the beach than normal living in Kanagawa.

Anyway, I have noticed there's a small minority of Japanese men wearing scandalously tiny bikini bottoms with like a g string back and not much else. I would characterize Japanese as generally modest people so I was quite surprised to see that.

Is it a new thing? Been happening forever? Have to do with sexuality or something?

By the way I'm not judging I'm just curious as it's not what I expected!

Any info would be interesting.

Thanks 👍