Iku Iku ♡ Succubus Saikyouiku: Rakudai Inma no Koukan Ryuugaku Nisshi

Based on the erotic game by DWARFSOFT.

Busujima, a middle-aged teacher with an insatiable sexual appetite, is sexually harassed just for watching a female student at a club activity, and is summoned to the school principal. During the lecture, a mysterious door suddenly opens, and a girl who looks young but has enormous breasts comes out, wearing clothes that are practically naked. Introducing herself as Lima, she is actually a succubus who has lived for hundreds of years, and holds a high position in the Succubus Kingdom. Busujima is surprised, and she tells him to become an instructor for the failing succubus exchange students. Then, saying it's an aptitude test, she suddenly presses her erotic body against him and begins masturbating. Somehow, he manages to endure and passes the test, and is introduced to two failing virgin succubus, and he decides to teach them all sorts of things...

(Source: Parabook, translated)

Note: Includes 3 extra chapters in the digital limited edition.