Doukyuusei Kaizou ~Namaiki Musume wa Jikkendai ni Shiteshimae!~

The student protagonist, Kagano Takeshi, studies intensely every day with the goal of earning his doctorate in biology. Looking down on his classmates for their superficial conversations, he spent his time in silence at home, immersed in his own experiments.

One day, Kagano development of a "cell rejuvenation drug" completed. When he tested it on mice, the cells did not actually rejuvenate; instead, their chests swelled and the females developed organ-like growths resembling reproductive systems. Furthermore, they appeared to be in an abnormal state of heat. Although there were no lethal side effects, Kagano was disappointed.

His frustration then turned toward Miki, who always teased him.
"I'll make her drink this drug."
And so began Kagano's experiments to modify Miki.

- edited mtl from official site