I guess in ch.3 the doctor say the uke already pregnant before the accident...and the reason the uke lie with that women because he to scared to start relationship with someone he want to reject but he dont want to burden his parent...
They find out it's Kanata's kid in ch 4 (specifically pages 20-23). As to what he lied about. Basically Shoma didn't tell her about Kanata. When he was breaking it off with her, he said he was getting transferred overseas, rather than telling her straight up about how he didn't want to marry her (he said she was too good for him) and about Kanata's existence.
wat ch did they find out it’s the seme child and not the women. also what did the uke lie about to the women? i’m too scared to read chapters 1-3