Not sure, but looks like Arsene has stolen several hearts: It's shown as a tally on his shoulder!
(Real talk, people's hearts are probably imprisoned by the "evil force", and we have to infiltrate and free them. Seems fairly straightforward to me).
I think they've already more or less confirmed its not going to be straightforward in quite that way.
New characters "rougher around the edges" than their predecessors. "On the run for doing what they think is right."
http://gematsu.com/2015/02/persona-5-director-discusses-characters-themes-development
Bolded = key word