Available from May 7th, Mementos are entirely optional, although we’d recommend that you don’t ignore them completely as they serve some useful purposes. Their intended purpose is to be home to “Requests”, small problems for the Phantom Thieves to tackle that you pick up in the overworld, and these problems are then solved by killing a particular enemy in Mementoes. Without spoiling specifics, it might also be worth keeping on top of them to help with the final dungeon, though you won’t miss anything or suffer if you opt out of doing any of them at any point up until the end. In addition to the Requests Mishima gives you, there are a few additional ones that require some legwork to acquire.
Ichiko Ohya, Tae Takemi, Sadayo Kawamaki, and Chihaya Mifune will each give you a Request between Rank 7 and 8, and you will be unable to Rank Up with them further until you’ve dealt with their Request. Take jobs in the Convenience Store and Flower Store in Shibuya and work four shifts in each.
Need more help? Our Persona 5 guide and walkthrough features a complete month-by-month summary with important dates and Palace strategies, as well as how to get the True Ending. Elsewhere, learn how to make the most of your free time with all Confidant, Social Link and romance options, the best ways to increase Social Stats such as Knowledge, Guts, Proficiency, Kindness and Charm, create the best Personas through Fusions, how to cheat on exams with our test answers, how to get Mementos requests, unlock the entire Trophy list and learn about the upcoming DLC schedule.
You can either tackle Requests as and when you acquire them, or save them up and deal with several at once. Given that the game runs to a schedule we’d recommend taking the latter option and waiting until you have at least half a dozen stacked up before taking them on. Don’t stockpile too many, though, or you may end up running out of supplies while you’re there. If possible, visit them when it’s raining in the overworld; it ramps up the difficulty slightly, but it increases the chances of loot drops and treasure chests, gives you a little more money and EXP, and makes Treasure Demons a more common occurrence. Unless you want to grind we’d suggest leaving a floor as soon as you’ve cleared out any designated targets in order to save resources - the deeper you go the larger the areas to explore become, but safe rooms are few and far between so you don’t want to find yourself caught short and miles from safety.