In Persona 5 Strikers, the Phantom Thieves have returned to contend with a devastating Change of Hearts Epidemic. Through the use of a mysterious new app that is allowing Metaverse navigation, Jails are arising with Rulers who are stealing the desires of citizens. Framed for the epidemic by an overeager police force, the Phantom Thieves must change the hearts of the Castle's rulers and restore the desires of everyone afflicted.
Having conquered the Shibuya Jail and changed the heart of Mad Rabbit Alice, the Phantom Thieves set out for their next goal: Sendai. Here they discover an author, Ango Natsume, is the ruler of the Sendai Jail. Natsume has used his influence to become a best-selling author, but in actuality, it masks a deep-seated inferiority complex and rampant plagiarism. With his fans ever more rabid, the Phantom Thieves infiltrate Sendai Jail to change his heart and put a stop to his scheme.
First Infiltration
In the Sendai Jail, you'll want to make sure you bring a team that has access to Ice, Bless and Curse abilities, as well as Physical, Gun and Nuke to capitalize on Technical Attacks. The team will note that there is a large tower in the distance and set out for it on the assumption that it's Natsume's Castle. On the way to the Castle, there will be the usual cast of minions. Once past all of them, you'll encounter Doma, a mid-boss variant of the Jack-o-lantern enemy who is guarding the castle gate. Morgana's Wind-magic is an excellent counter for Doma, and combining them with follow-up attacks will melt Doma's bar in no time.
Rather than being defeated, Doma flees and the Thieves are teleported away, with their ability to exit the Jail from a checkpoint removed. The Thieves find themselves in front of the tower but have no path forward. With security too strong in the front, the thieves must sneak into the back, where they'll discover the Gate of Trials. It requires three proofs of victory in order to open. After discovering this, exit and follow the exclamation mark on the map. This will lead to the first proof, which is behind a door that requires "an offering of Sun and Rain." A novel from Natsume's novel mentions two orbs, so you're off in search of the Sun and Rain Orbs.
The First Core
To find The Sun Orb, head back to the main path and you'll find a raised drawbridge to the Eastern side. To get around it, you'll need to go to the Northern side of the map and hop across the columns to reach the rooftops. Now the Phantom Thieves can hop down to reach the park. Here, there will be a river with stones that can be used to jump across to the other side. Make sure to follow the side path of rocks as well to find a chest, though.
On the other side of the river, climb the steps to pull a lever that will activate the draw bridge. There you'll find a suspicious-looking temple holding the Sun Orb within. Taking it will trigger an ambush of shadows, but you should be able to make quick work of them (especially if you drop the hanging chandelier on them for extra damage). After collecting the Sun Orb, you'll be able to lower the draw bridge to make traversing the area easier. Moving toward the west, Doma will return for a second battle. Doma will flee again, but your checkpoint exits will be reactivated.
With Doma defeated, head straight on into the West Garden. In the West Garden, investigate the front door of the shrine, which is locked. Then climb up to the third floor of the apartment building facing the temple to reach a checkpoint and a mini-boss encounter with Prankster Leader, a variant of High Pixie. Continue following the rooftops, being careful to avoid the searchlights and break into the Rain Temple from above.
Much like the Sun Orb, taking the Ominous Rain Orb will trigger an ambush. Clear out the shadows and you can exit the afront door of the Rain Temple, then take both orbs back to unlock the door and access the Prison Keep, which triggers a battle with another mid-boss, Ante, a variant of the Lamia enemy. Use Ice attacks to stun her, and make use of the ice crystals nearby. Be prepared to jump over her Maragion, which will cast a ring of fire upon impact. You can use the Gargoyle statues to dodge Ante's attacks and then counter with a Lunge. Once Ante is defeated, climb up the stairs of the keep to get the first proof, a copy of Natsume's novel, Prince of Nightmares, which is also a Core.
The Second Core
From the Keep, return to the Land of Rain and continue beyond to Aoba St 1st Ward. Upon entering the 1st Ward, the Thieves are confronted with a gated hallway that mysteriously opens on its own. At the end of the hallway is a mysterious light, which is a Red Orb. Use Joker's Third Eye to see spotlight traps that are hidden and sneak your way to the Red Orb, shooting any Spotlights to prevent being attacked. You'll still be ambushed once you collect the Red Orb, but it's nothing you haven't faced already. The Red Orb will open a new door in the hallway, which opens a path to Blue and Yellow doors.
Explore the newly opened area and you'll find the Blue Orb, which will open the corresponding Blue Door. Once the Blue Door is open, explore this new area along the rooftops to find the Yellow Orb and defeat a final ambush of shadows. The Yellow Orb will open its corresponding Yellow Door, which leads to a Hacking Door mini-game. Protect Futaba while she hacks the gate, then enter the Prison Keep and you'll face another mini-boss, Kuga. Kuga is an Orthus variant, so again you'll use Ice attacks. Once Kuga is down, ascend the Keep and collect the second Core, a Soukaisha Trophy.
The Third Core
With the second Core obtained, slide down the pole to quickly exit and make your way to Hirose St. This area is teeming with security cameras, so be careful not to be spotted. Go through the next building and disarm the suspended traps, then defeat the Slime mini-boss. Climbing up to the rooftops, you'll cross some pillars and find a seemingly unpassable area. Using Third Eye, you'll notice some hidden platforms which will help you get across. Then jump across more floating pillars and go around to the top left most corner of the map and drop down.
Look down and cross the transparent floor to reach a small platform. Open the chest to loot the Ann's Skin Ripper whip, then backtrack and head down. Cross more transparent floors until you reach the building to the South. Here, defeat the enemies, then drop down and cross the transparent floors on your left. Cross the wire and the last of the transparent floors to reach the Prison Tower and a battle with Betero, who is an Eligor variant. He's weak to electric attacks, but make sure to watch out for his lunge attack. Once Betero si downed, climb up and conclude the final Core, a Gaudy Fountain Pen. With all three proofs obtained, the Thieves will suggest it's time to fall back, ending the first Infiltration.
Second Infiltration
Before returning to Sendai Jail, Sophie will reveal she has detected lingering shadows in Shibuya Jail. Complete her request to investigate lingering Desires and unlock the ability to revisit previous jails. After completing this, you'll receive a few other Requests as part of a tutorial, which can net you some items and improved gear. Once you're completed with these, it's time to return to Sendai Jail.
Once back in the Metaverse, use the three proofs to open the Gate of Trials and fight through the waves of enemies. Eventually, you'll encounter another mid-boss, Doramu the Loyal, which is a Pisaca variant. Fire attacks will melt his Down gauge, and you can use the sword monuments to dodge and reposition. Once Doramu is downed, you'll find a T-shaped passage with a ventilation hole. Use Third Eye to locate the vent and then head through the main entrance to Natsume's Castle. Make sure you're stocked up on supplies and fight your way through the castle until you reach the roof.
Upon reaching the Roof, the Thieves will discover another Birdcage, but also another Trauma Door preventing access. Natsume's threat to the real world isn't diminished at all, but now that Sophie has been able to detect the source of his trauma, the Phantom Thieves are one step closer to changing his heart and returning desire to the citizens of Sendai.