Sadism overflowing from beneath his smock Vol.4 (TL Manga)

Asahi is a doctor in training who reunites at a hospital with Yamato, her classmate from middle school. Yamato used to be nice, and they promised that they'd become doctors, but for some reason he's transformed into an unbelievably cold-hearted heart surgeon... "I'll train you," he says, and starts to teach her medicine know-how, but then adds: "I need to relieve some stress. You can pay me with your body," then suddenly gives her a long deep kiss just a like a lover would! What is Yamato planning!? Vol.4, 50 pages.