This is one of those weird things I've been thinking of as of late. Ever since I first read Corpse Party Musume, I felt the worst for one specific character, Miyu Shinohara. Won't spoil what happened to him (Yeah, Miyu's a boy), but it was one thing such that it makes you really wanna get revenge for the events of Musume. Problem is, how does one do that in a series where combat is virtually non-existent?
Well, we introduce a spinoff that's not exactly Corpse Party, per say. At first, I was going to simply name it Yuki Shinohara's Revenge due to how the concept felt like due to how the premise of the story was of the titular character, Yuki Shinohara (more on him later. Yes, he's a trap like Miyu too), intentionally trying to find his way to Tenjin/Heavenly Host in order to avenge Miyu and the others while also referencing a non-canon sequel of Metal Gear known as Snake's Revenge. Then I realized this game would play so much like Metal Gear that I decided it should be called Corpse Party Solid: Yuki Shinohara's Revenge (or simply Corpse Party Solid).
Since this is its own universe, I should highlight a few major differences between it and Corpse Party canon. They are as follows.
1. In this timeline, Seiko Shinohara and Miyu Shinohara are siblings, with the titular character, Yuki Shinohara being Miyu's identical twin brother. The birth order is such that Seiko is still the eldest, followed by Yuki (legal name Yukina) then Miyu (legal name Miyuki), and finally Yuu.
2. Yuki disappears along with his mother, Sayaka Shinohara, six months before the events of Corpse Party Musume. Seiko, Miyu, and Yuu believe Yuki was kidnapped by their now-AWOL mother.
3. The events of Musume take place while Satoshi Mochida and crew are in their first year of high school at Kisaragi Academy. Seiko is also caught in the mess.
4. Seiko manages to briefly rescue Naomi following her capture and sending Yuka to find help. Their storyline from the original Corpse Party plays out, complete with the two having a big fight that splits them up. However, unlike in the original, Seiko's death is that from Book of Shadows, where Naomi succeeds in rescuing her from being hung to death, only to run in fear of Naomi and end up decapitated by piano wire.
5. The events of Musume end with Ayumi Shinozaki and Yoshiki Kishinuma being the only survivors. The now-peaceful Sachiko Shinozaki, for reasons unknown, decides to create a 'copy' of herself named 'Sachiko Two' before ascending to the afterlife. Sachiko Two, for some inexplicable reason, foresees herself 'rebuilding Yuki Shinohara' despite not having met him yet.
6. One year after Musume, Yuki Shinohara is revealed to be alive. Upon returning to Kisaragi Academy, Ayumi and Yoshiki note his personality had changed from a girl-loving, crossdressing pervert to a distant, angst-filled wreck. They soon learn from the heterosexual trap that he had become brainwashed into becoming a child solider and that it was only by chance that he survived a shot to his now-missing right eye and the left side of his forehead. He tries to adapt to getting back to a normal life, but continues to suffer from Post-Traumatic Stress Disorder.
7. Yuu Shinohara, the younger brother of the late Seiko and Miyu, along with the still alive Yuki, arrives in Kisaragi Academy to bring Yuki his briefcase (unaware that it contains a MP5K and ammo for it). He meets up with Ayumi and Yoshiki, who are terrified to learn that Yuki intended to use the Ritual to enter Tenjin himself. They try to stop him, only for Yuu to accidentally drop the briefcase--never learning what was inside it whilst his trappy nii-san disappeared into the darkness.
(Originally I was going to have Ayumi, Yoshiki, and Yuu end up in Tenjin with Yuki, but in the end I couldn't get it to work due to Ayumi and Yoshiki already having been there and done that back in Musume. Was bummed out when I scrapped that idea as I really wanted to give Yuu Shinohara a bigger role in Corpse Party Solid too.)
As for what the gameplay would be like, it's essentially Corpse Party under the same game engine as Metal Gear Solid: Peace Walker. This means you're no longer playing from a top-down view, but a behind-the-character third-person view. The major differences are as follows:
1. When aiming, the camera hovers over Yuki's left shoulder since he is left-handed.
2. Holding someone via CQC Grab from behind allows for three options. Interrogate, CQC Throw, or Eye Stab with the Bowie. The eye stab was never present in any Metal Gear game, its closest equivalent being the throat slash.
3. Weapons are found in-field like in MGS1 through 3, but unlike said games, cannot be used immediately. Instead, Yuki must radio for Sachiko Two's 'pet tentacles' to pick them up for R&D purposes. (Sachiko Two explains this necessity as something that would allow Yuki to fight off paranormal beings.)
4. In-game gore is more or less limited to blood due to prevent the game itself from being banned in Japan. (Ex: Getting shot in the head will have the victim cry out before dying--just like in the Metal Gear series.) However, manga slides that take serve as cutscenes will feature more gore to make up for that.
That pretty much wraps up the backstory and gameplay concept. Up next is the character concept for Yuki Shinohara, the identical twin brother of Miyu Shinohara who is pretty much the focal point of this game concept.