Euh? I'm pretty sure the author discussed about this in the earlier chapter. It did say that they used a sperm donor system thingy (σ≧▽≦)σ
Read ch2 again then u will understand rourou is seme biological child in fact rourou is born by unknown paid foregin women with seme sperm at the time seme worried about his child's safety so he change uke sperm with his and made uke believe that rourou is his child and let uke raise him hope u understand my explainations
Read it from the start again, the author explain everything from the start..
Ah i did re-read it definitely made me understand a lot better thank u ヾ(❀╹◡╹)ﾉ~
im kinda confused about Rourou like who is the mom? How did yiyi get custody? Is Rourou adopted? even if he is it still doesn't make sense cus Yiyi isn't eligible to adopt in the first place n the main reason is cus his job is not stable i- does nobody remember having sex or is rourou made outta magic cus this don't make no types of sense (￣∇￣")