Complex sentence: Kyoko then vowed to never again disregard Tohru for whatever reason; she raised Tohru by herself, not to mention the care she offered Arisa Uotani and Saki Hanajima, Tohru's best friends.
Split into simpler sentences: Kyoko then vowed to never again disregard Tohru for whatever reason and raised Tohru by herself. Not to mention the care she offered Arisa Uotani and Saki Hanajima, Tohru's best friends.