The most explicit sexual description in [Chunbyeon Punggyeong] serialized in 1936-37

‌However, finally one night, unable to endure it any longer, he succeeded in lunging at his fourteen-year-old husband, who had been sleeping soundly beside him for several days, and stealing his lips.
And with that, having further stoked the flames of lust, when he threw his feverishly heated body upon the boy's thin and small chest,
the immature child easily woke from his sleep and, terrified without knowing the reason, ended up running to the main room in tears.
And after that, no matter how much his father-in-law tried to reason with him,
the boy stubbornly refused to return to Geum-sun's side......
- Park Tae-won's [Chunbyeon Punggyeong], pages 132-133
He = Geum-sun (seventeen years old)
He is a fourteen-year-old boy, which is unexpected.