Well.

His clan gave him the dirty job of spying on a deflected clan member. He and another member were told to spy and bring back info. It didn't work out too well because his buddy got devoured.

By Nellsa, who in turn bit through his leg.

She didn't know they were spying but knew they were trespassing in her territory. (She's calmed down a lot!)

He sarcastically apologized aboug being in her space and she assumed he was serious and nursed him back to health.

Because most people just argue with Nellsa than admit they were wrong.

Keikai had never really had nice affection done to him, and clung to it greedily. He is constantly about making Nellsa happy. He takes her for walks, throws her favorite toy for fetch, and lures his own father for her to eat. He absolutely loves her.

He has quickly accepted her quirks and is probably the only person who possibly knows Nellsa and how she thinks. It helps that also accepts him and his horrible, horrible flaws.