male with breasts
だが男だ 男子おっぱい ショタ巨乳 busty_boy bustyboy
Pretty self-explanatory, the character is biologically male and may even self-identify as male, however his appearance may seem as more androgynous or even feminine and, most importantly, he somehow has female breasts.
Use this tag when the character has no penis or testicles visible, otherwise it should be tagged as newhalf.