These are the kind of phrases used by boys in anime and manga aimed at kids, expressions used by young boys who want to have adventures and who yearn to become strong warriors. For this reason, there are lots of decisive-sounding expressions aimed at self-encouragement, such as 「~nda」 and 「~mon ka」. On the other hand, the character's childishness is shown in the expressions they use when they get upset with adults, suddenly become scared, tease friends and so on.