Kairi is also Lea's little sister, so odds are they will know each other too. I also giggle at the fact Senku has good luck and Allen's power was bad luck.
Hm . . . Senku and Lapis have a common thread in painting. Maybe she's either been learning from him or they exchange tips or he got her into painting after her bout with villainy? Also always open to Demyx, though I'm not quite as sure what there.
Also, I find it very appropriate that he'd be teaching watercolor.
Jasper might be more willing, but.