It does in fact say "Tenu". Tewi would be てゐ. This error could be a deliberate joke (that I'm not getting) based on the similarity of the ゐ and ぬ characters.
Looking at the Tenu note, I see that many people fell for the trap.
ReimuThe next day.Hurry up and make them!Hoooh-hohohoh!Come on now, are you hesitating?A doll of the classmate you hate the most!If you don't finish, I'll make it homework!Wa— waaaaaaaaah!Submission displayTenu