It doesn’t matter what day you do this as long as you do it before the deadline. Here are some things you should consider to help with your schedule management.
Take note that once you sent the calling card, the whole castle will be on full alert at 99%. You can still lower the security level by defeating enemies but there’s almost no way of lowering it all the way down. You can still do some last-minute farming and training but you have to keep an eye out of your resources and supplies. The castle will also disappear after completing it so if you want to get particular personas, make sure to try getting them before clearing the palace.
When ready, head to the treasure room via the same route you took last time to trigger a cutscene. While attempting to carry the treasure, the man himself will appear. After a few more dialogues, he’ll transform to an apt depiction of his corrupted being.
For the first couple of turns, save your SP by performing normal attacks only. This will force him to use Libido Boost to heal himself. After that, concentrate on attacking the trophy to destroy his source of healing. Make sure to counteract his Lustful Slurp (attack boost) with Ann’s Tarunda (decrease attack) to avoid getting heavily damaged from his attacks.
After destroying the trophy, the boss will be vulnerable for an all-out attack. Your team will do it automatically to deal heavy damage. Next, you need to perform a special strategy in order to steal the treasure off the boss himself. This includes sending one of your teammates to sneak to a good position while the others are drawing the boss’ attention. Ann is definitely not an option since the boss has its eyes on her. Morgana is a good option but that means removing access to Media, an all-party healing skill. However, if you have access to your own healing skills, you can you can send Morgana and take care of the backup healing. Ryuji can be sent without any repercussions since you don’t really need offensive power while you’re executing your strategy.
Whoever you decided to send, keep attacking the boss for a few turns as your ally gets into position. Once in position, your ally will successfully steal the treasure if you’re able to draw the boss’ attention long enough. This will severely affect the boss, immensely lowering its defense and preventing it from attacking further. Exploit this chance to unleash your most powerful attacks until the boss is defeated.
After the scenes, you’ll be back in the real world. Congratulations for clearing this castle! If you managed to clear the castle before the deadline, you can now take it easy and concentrate on improving your Confidants and social stats.
Spoiler: