You were Natsumi and Fuyuki's older sibling. You had met a couple of the frogs, that being Keroro and Tamama.

Fuyuki had called you in a panic. Apparently the two frogs and their friends went out on a mission or something and came back all weird and stuff. So, being the good big sibling you were, you went over. A tall built man answered the door, looking in pain and panicked.