> This answer is probably in the manga, but's tough (
> to me ) find the mangas,
> so I've only seen it till n3. Anyway, why does
> keichii signs K1 in the
> message for belldandy?

It's just a fashionable short-hand for the name
Keiichi. The "Kei" part can be abbreviated by the
English language letter "K", the "ichi" bit by "1"
since the Japanese word for the number 1 is "ichi";
hence K1 = Keiichi.

Sam the man