This Young Beast is Like a Forbidden Fruit Vol.3 (TL Manga)

Yui and Kei lived next door to each other when they were young, but they had to be apart after an incident…Several years later, destiny leads them to find each other again…
"I've always loved you, Yui," says Kei as he kisses her abruptly. His true love opens up her body little by little, but there shines an engagement ring on her left hand...
Vol.3, 42 pages.