Seiken Tsukai no World Break, Gakusen Toshi Asterisk Recommendations
Both conatain Ecchi and Harem with very similar kind of duels, characters and their training in world known academies.
A purple-haired protagonist with lots of combat potential transfers into a prestigious combat university. The schools from both anime are structured the same and the fights that take place there between students are very similar also. They each have an ecchi element to them while being a mix between action and slice of life.
This anime is similar in the swords/weapons style. Seiken is based on past lives and gakusen is more of the users current ability. Both male protagonists are special and strong. They are both surrounded by many females who in a sense fight over the main character. Both also take place in somewhat of a school setting.