Maybe I read wrong but I'm sure the main guy was in his third year of middle school which means he was at least 15. It doesn't change the fact that it was unerage contact but I just feel like 12-13 is very different from 15-16. BUT I totally agree that its still very pedo-ish of the biological mom to willingly have sex which a minor! A bit disturbing actually, I had to pause myself from reading for a second to process it and give myself the OK to continue reading. But Aside from that, I totally loved the manga. A very unique plot which I can appreciate!
Both MCs are in their 2nd year of high school when Raichi turns 3. Which means Tetsu was 13-14 when Raichi was born and "Sachi" was then 20-21 (considering she was 7 years older than Tetsu).
So yeah, despite this being a good manga and a good story, this was, to say the least, disturbing. Let's call it as it was, an adult taking advantage of a kid. Because no matter how big or mature 13-14 year olds can be, they're that - kids. And she was a student teacher. Basically money-earning adult. Interestingly, in the manga, no one seemed shocked or creeped out by it, they were rather much surprised by the fact he's a single dad. And that really sad.
Was it a good manga? Yes. Was it wild from start to end? Hell yes. It's well written, interesting, good characters, story was told in a great way. Its not so much that the manga is bad so much as it is the actual characters are, a pedo rapist mother, a cheating boyfriend, and a rival love interest who could have had such a bigger and amazing role in the whole thing that would have made the story even more interesting than it already is. He had a really small role even though he seemed to have had a really interesting story line but the author kinda rushed him. Don't even get me started on the pedo mom, this isn't the first time I've read a manga where the older women go after the young guys and magakas always try to make it seem less creepy by making the 12-13 year olds look like they're 16 year olds. It doesn't make it any less creepy, sorry. I won't act like despite all those weird aspects this manga wasn't good, because it definitely was tbh. Also Maeda is gay don't @ me.