This でな is indeed the te-form of だ, followed by な, a masculine sentence-final particle. A sentence-end で can have several different roles. Here, it may be a reason marker (i.e., explaining to someone why he has a sweet), in which case the combination of で + な roughly corresponds to "you know" in English. Or it may be a simple "continuation marker". As this ...


"oboe ga aru you ja no", means "you seem to remember." "no" in this phrase has no negative meaning.

Only top voted, non community-wiki answers of a minimum length are eligible