You only played as Kafei in one sidequest in Majora's Mask, but it was interesting playing as someone other than Link in a Zelda game. His story and motivation also made him compelling enough that he could have just as easily acted as the game's protagonist imo.
Shep Seere from Heartbeat is a tanooki and a traveling merchant. Despite tanookis' reputation as pranksters and her mischievous appearance, she's actually a pretty cool person and just wants to make an honest living.
Technically the majority of party members in Heartbeat are temporary, but she only fights alongside you during a couple of battles in the main story. Post-game you can have her (and everyone else) in your party as much as you want. At that point, you can just buy stuff from her whenever and wherever you feel like.