Yes, Jiraiya loves her. However, Tsunade does not love him back in the same way. While she would likely give her life trying to defend him, she has no romantic feelings towards him. This can make for either a great or an awkward couple of cosplay, depending on how you roll with it.  Jiraiya and Tsunade is the best option for a couple's cosplay in my opinion. Dan, Tsunade's actual love interest, did not get any meaningful screentime and has nothing that makes his outfit stand out. It would be a long night of nobody having a clue who you are cosplaying as if you are going as Dan.