This was likely due to elements of the storyline involving the Shinsengumi (a group who guarded Kyoto during the end of the Tokugawa Shogunate), of which all Japanese are very well-acquainted as well as the Chushingura (Treasury of Loyal Retainers) and Mito Komon (the stories on Mitsukuni TOKUGAWA, a lord of Mito domain in the Edo period), so there were no issues even if the story presented these personalities and behaviors on the assumption that they were common knowledge.
その理由として、新選組という設定は日本人には忠臣蔵や水戸黄門と同じく馴染み深いものであり、登場人物の性格や行動様式を周知の事実としてストーリーを展開しても違和感がなかった。