no romance either no kiss nothing ..bad
I would consider it as yaoi just because of the last extra chapter. Even though it's not a real "scene", there is an explicit moment that shouldn't be in a shounen ai.
This is the order that you need to read it in:
Sangatsu Boujitsu, Kuma Wo Hirotta
Rokugatsu no Hengen-san
Shichigatsu no Kousaten (incomplete)
Then you will understand why it is considered yaoi
Here are the explicit sex pages:
http://www.mangago.zone/read-manga/rokugatsu_no_hengen_san/tr/117757/page/31/
http://www.mangago.zone/read-manga/rokugatsu_no_hengen_san/tr/117758/page/11/
We usually call R18+ BL manga: yaoi. This manga fits the classification.
If you want to read a manga with more explicit sex scenes I recommend you to look for the Smut tag. And a really good one and by this same artist (Takao Hiroi) is http://www.mangago.zone/read-manga/ikenai_otoko/
It's about AV actors. It's hot!
no sex included its not yaoi