Monogatari no Naka no Hito
The story of a young noblewoman wishing to learn magic like the anciant time and a mysterious magician wishing to learn modern magic. Basically he use magic like the ancient magic so he ask her, after saving her, to teach him modern magic and since she is a student at the magic academy, he changed his appearance to look younger to accompany her there.
Boundary Labyrinth and the Foreign Magician
Harem as fuck. Classical plot, bit cliché but ok. Bullied by his half siblings, Mc remember his past life. This new world is similar to a VRMMO he used to play back in Japan. Realizing he can use his magic has in the game, he set off for an adventure far from his noble family, together with his trusted maid, a (strong) half vampire.
Jichou shinai Motoyuusha no Tsuyokute Tanoshii New Game
Was send by truck-kun a 1st time as the hero, won, reincarnated as a company slave again and died again. Asked to be send back to the same world but this time he will leave without restrain. Dropped Ecchi/smut harem. The girls have cliché personalities and he doesn’t even really care for them. OP Mc is a bastard but that’s ok. What I have a problem with is: where is the plot? He is just running around gathering an harem to fuck and that’s all?
Eden (tsuruoka Nobuhisa)
Players have been trapped in Eden, a VR game. 3 years later, Mc is the only one still training the beginners skills only, mocked by the other has the "instructor". But his persistence might be the secret to become the strongest. Almost dropped at the beginning but became more interesting, as serious plot appeared. Mysteries with death threat and serious theme manga.
Isekai Onsen ni Tensei shita Ore no Kounou ga Tondemosugiru