FIFTY-plus hours in and I think my team is slightly OP-ed (they are on average Level 50+ so I've been progressing at a pace of one level per hour!!!) Have killed all the bonus bosses(!) but am still getting the hang of the persona fusion mechanics. Thanks to walkthrough tips though, I created "Black Forest", which came in handy to destroy the last story boss (he has a skill that boosts power attack x2); even then, the battle took me some 30 mins!!! Will now unlock the last playable character, which should be fun.
(am sure she is singing in English but it sounds Japanese)