According to manga updates it is serialized in Kakao https://www.mangaupdates.com/series.html?id=154643 So toon: https://page.kakao.com/home?seriesId=52902073 novel: https://page.kakao.com/home?seriesId=52224084 Not that there is a shortage of novels like Only I level up...
To be honest, I could’ve sworn there was a similar one to it. Protagonist fights a OP Dragon and then uses reincarnation magic but unfortunately, it was different.
Yes the one you're talking about is "the Ex strongest swordman long for magic in another world" or something like that
https://www.novelupdates.com/series...-sarani-tsuyoku-naru-tameni-tenseishimashita/ Welcome. Nope, the DRAGON uses reincarnation magic on the hero.