Search gender: all male female オンセイ Japanese Boy Names Variations. 1 names found. gender: all male female Name: onsei Katakana: オンセイ 0 Kanji: 恩誠 Meaning: 恩Debt of gratitude 誠True. A heart without lies and falsehoods. Sincerity. Truly. You can save your favorite names with NAZUKE PON > About Japanese Names > Search Japanese Names By Kanji > オンセイ Japanese Boy Names Variations.