One piece: is a anime of adventure and pirate fighting. It has 929 chapters, I think you will have more than enough to pass the quarantine hahaha. It is the best-selling manga in Japan, I have been following it for 15 years and I think it's great. I know you can be lazy because of the number of chapters, but you will not regret it, I assure you.
High Scholl DxD: The story stars Issei Hyoudou, a high school sophomore boy who has been murdered by a girl on the first date of his life. Issei reincarnates as a demon, and from that same day works as a servant of Rias, a demon girl of the highest level who turns out to be the most beautiful and popular in the entire institute.
It is an adaptation of one of the best-selling novels in Japan, it has four seasons, although the third is a bit bad because the novels did not follow. He is of the genre echi and harem, but also has a good history and very good fights, also with a perfect harem. If you finish the anime and want more, I recommend the novels, they go for volume 30 and on.
Mahouka Koukou no Rettousei: It is another adaptation of one of the best-selling novels in Japan, it deals with a school of magic stucco, it is harem, but not echi, but it has a history and explains very well the use of magic.