>>955045
Holy shit you're sort of right. I have a txt of it so I skimmed through it but I didn't see anything about pregnancy or any incest stuff in the other short stories either. So I google'd for a bit and found a jap blog post pointing out this sentence:
思わず二人体を寄せあって、節子のむき出しの脚を下腹部にだきしめ、ふとうずくような昂《たか》まりを清太は覚えて、さらにつよく抱くと「苦しいやん、兄ちゃん」節子が怯えていう。
Which is moonspeak for:
Inadvertently, their bodies became pressed up against each other with Setsuko's bare legs against his groin. Seita became aware of a sudden throbbing swell; when he pressed harder against her, Setsuko frighteningly said, "That hurts, big bro."
Apparently, in his novel 骨餓身峠死人葛 there is full on brother/sister incest. I just remembered before posting this that there is an official English translation from Japan Quarterly:
Unconsciously the two drew close together, he squeezed her naked feet into his abdomen, suddenly Seita felt an aching sense of excitement, clutching her even more tightly, "you're hurting me, Seita," Setsuko said in fright.
In my amateurish opinion I have to disagree with this translation. 脚 is used for the legs and 足 for the feet, 下腹部 matches specifically to the hypogastrium which is a region of the abdomen, but not the abdomen itself. In the next sentence he writes they can't sleep so they take a walk and piss. So I guess it's left open whether he got an erection from his dick pressing against her vag or he was merely using his sister's legs to hold in his piss. I find the former much more probable.