Tsubaki was Mizuki's girlfriend, and she remembers him being genuinely kind before Orochimaru pulled him into his orbit. That connection basically ruined what they had. When Mizuki breaks out of prison, Tsubaki actually helps the authorities track him down. During an interrogation where she confronts him about harboring a grudge against someone who sacrificed everything during Orochimaru's attack, Mizuki loses it and knocks her out—making it pretty clear he's moved on from whatever feelings he had for her. After his defeat, Tsubaki worries to Iruka that she might face some legal fallout for her involvement with Mizuki, which is fair enough considering the circumstances.
Content compiled by AnimeList.moe from publicly available sources.
