He changes into something bigger when he has to fight.

[Takeru reaches out to gather Patamon up in his arms, looking down to address his partner and get a better view of the sweater.] But it's not like you've gotta worry about that while we're here in the base.

[He turns his attention back to Makoto.]

Thanks a lot for your help. If it's as simple as you made it look I think I can get the hang of it.