Magika no Kenshi to Basileus, Rakudai Kishi no Cavalry Recommendations
In both mangas, there is an academy people attend where they can practice "sword skills" (swordsmanship). The protagonist of both mangas seemingly has a shrouded past (in Rakudai, some of his past has been leaked). Both protagonists also are surrounded by a group of girls (a harem) who may have feelings of affection for him. There is a "little sister" in both series, who come to see him (part of harem in Rakudai, attacks him in Magika). If you've liked one series, you may enjoy the other.