Act X: The Boy In Red Arc
For the duration of this Arc, malevolent spirits will be running amok all over Tenjin. They will attack both Yuki, Naho, friendly ghosts, and even New Humanity terrorists on sight and must be taken down lethally. At the same time, New Humanity will be on the lookout for the former child soldier and as a result, the entire Act is played on Full Alert status.
The goal of this segment is to keep up with Yuka Mochida as she tries to lead our battle-hardened trap protagonist to the rooftop, where the ghost of Naomi Nakashima is currently locked in battle with The Boy In Red. Of course, it's not that easy as for some reason, Tenjin itself is beginning to fall apart, with staircases and sections of floor collapsing. Best way to visualize this segment is that one segment from Max Payne 1 where Max has to escape a burning building that's exploding all around him.
Eventually, Yuka, Yuki, Naho, Sayaka, Seiko, and Miyu reach the rooftop where they see Naomi fighting against The Boy In Red--the one who was formerly their close friend--Satoshi Mochida.
Boss Fight: The Boy In Red (Satoshi Mochida; 3rd Encounter)
At the start of this fight, the ghost of Naomi Nakashima is considerably weakened. Yuki and crew find her pleading to Satoshi that she was not the one who killed Yuka, with the one who was formerly Satoshi-kun replying "The visions I saw when I died don't lie~!" Yuka tries to step in and defend Naomi, begging for her older brother to stop, only for The Boy In Red to scream in rage. He charges at both girls, clearly blinded by rage.
The actual fight begins with Yuki Shinohara charging into The Boy In Red's path and swinging the Bowie in his right hand to fend him off. His Knife gets parried by what appears to be a trio of scissor halves rigged into a claw-like formation, and at this point our trappy protagonist must try and overpower The Boy In Red. If he fails, Satoshi will knock the Bowie out of Yuki's right hand and slash his right forearm open, taking out a good deal of health. If he succeeds, the scissor claw rig will break apart, with Yuki following up with a kick that sends The Boy In Red flying back. Yuki will draw his IMI Desert Eagle after this.
The Boy In Red will fight Yuki Shinohara in a similar manner to the first time he was fought--with underhanded splashes of blood to stun the battle-hardened otokonoko and the use of paranormal power to launch random objects from scissors and pencils to desks, cabinets, and random debris. The difference here is that Yuki-kun can utilize all of the weapons he has on him, and that both Naomi and Yuka will generate magic barriers to deflect some, but not all of the debris The Boy In Red launches.
Three-fourths of the way into the fight, The Boy In Red will begin to summon the same kinds of tentacles that Naomi could back when she was The Girl In Red. Unlike Naomi's, Satoshi's aren't used to block shots, but instead spear out of the ground at an angle to impale Yuki through the chest (insta-kill). Both Naomi and Yuka will call out to Yuki whenever they sense such a tentacle coming and Yuki must clear out of the spot he's standing in before it's too late.
Upon this Fight's conclusion, The Boy In Red will drop to his knees, gripping his sides in extreme pain. Sachiko Two observes this and informs Yuki and the ghosts of Naomi Nakashima and Yuka Mochida that Satoshi is actually trying to purge The Darkening from within him. She then yells at Yuki to get away from him, but before the latter can do so, The Boy In Red goes berserk. He takes a clawing swipe at Yuki's face, drawing blood from his right cheek and forcing him back.
The former child soldier readies his Deagle and Bowie to defend himself against the charge, only to see Yuka's little hand having ripped through The Boy In Red's abdominal area from behind and gripping his intestines--a complete reflection of Yuka's own death when a malevolent spirit disguising itself as Naomi did the same to her. The Boy In Red collapses onto his knees as a shocked Yuki and crew find behind their former foe a tearful and grief-stricken Yuka-chan behind him--still holding the entrails in her right hand. Yuka, Naomi, and Yuki gather around The Boy In Red as the Darkening finally leaves him, with his final words being "Be careful. The Darkening will corrupt you like it did me. It took advantage of how that spirit that killed little Yuka-chan made itself look like Naomi. Also be careful of that child soldier with the big gun..."
Yuki asks if Satoshi is referring to Colonel Thorne, but it's too late. Realizing he couldn't keep his promise, the former child soldier slams his fist on the ground as he curses while the ghostly Naomi breaks down hysterically over her inability to reveal to Satoshi Mochida how she really felt about him. Both are comforted by the still-grief-stricken Yuka Mochida, who tells them "Satoshi-kun is free now, and we can be together again." Miyu-chan asks if there was any other way this could've happened, but before Yuka can answer, Sachiko Two drops to her knees in pain.
The tentacle loli reveals she had sensed the Darkening grow in power to the point that it's already tearing the paranormal plane that is Tenjin apart, and that it would have to be contained in order to prevent that and their own 'erasure' from happening. She then uses her tentacle tails to pull out from a ground-based portal the Man-Pack Vulcan salvaged from the second encounter with the now-late Boy In Red, which Yuki arms himself with to buy the tentacle girl some time.
In the distance, the Darkening materializes as a horde of twenty-five large, demonic, manta-like mecha. They approach in waves.
Boss Fight: The Darkening (Mechanized Attrition)
Twenty-five real robots designed with manta ray-like features attacking you in waves--sound familiar? In case it doesn't, this is the Corpse Party Solid equivalent of the MP-RAY fight from MGS2, but with some minor changes. In place of FIM-92 Stingers, Yuki Shinohara will be using a Man-Pack Vulcan taken from the second fight against The Boy In Red, and that Sayaka Shinohara will be supporting with Sniper Rifle fire. Also, the weight of the Vulcan makes it difficult for Yuki-kun to move around quickly, but he can turn at normal speed to intercept 'RAYs' and missiles alike.
Anyways, the not-RAYs will attack in waves of three, with another not-RAY replacing one that has been critically damaged. They attack with Vertical Launch Missiles which must be shot down and wing-tip Gatling Guns whose strafing attacks must be stopped.
Upon the conclusion of this fight, Yuki-kun will drop to his knees, releasing the Vulcan's heavy ammo backpack from his being--all out of exhaustion. Sachiko Two will present the 'Pandora's Box' containing the Darkening, but then an earthquake hits. This quake is accompanied by a blinding light that, once it and the quake subsides, reveals that the building had completely collapsed. Yuki is the first one to regain consciousness as he finds his former CO and now sworn enemy in front of him, holding the container with the sealed Darkening inside.
This Arc ends with Yuki Shinohara gritting his teeth in rage as he comes face-to-face with Colonel Vincent Thorne, the child soldier-turned-revolutionary that became his enemy once more.