I don't really care about her at the moment.
One reason for that is because she isn't in his team.
Unless our Gantzers do their mission with the other team all the time from now on, why would we see her again.
But my biggest concern is that he'll fall for her. If she get's killed while he loves her he might use his points to revive her instead of Kei.
And I hold him responsible for reviving Kei. He himself said to Kei "I won't let you die Kei-chan. Besides....it's my fault you're here in the first place...I'll make sure you get home alive".
Which he didn't do so far. Not to mention that this was before Kato died and was revived by Kei.
Kato has a big debt to repay.
And Kei is the better fighter. The Ganzters need him.
"For Feanor was made the mightiest in all parts of body and mind, in valour, in endurance, in beauty, in understanding, in skill, in strength and subtlety alike, of all the Children of Illuvatar, and a bright flame was in him"