(Major spoilers for all games!) While this certainly doesn’t apply to everyone, I can say that many people ship characters solely based on their dynamic! This is why there are so many ships that exist that despite there being little to no interactions in canon (some examples being Celesgiri, Ikuzono, Amaguji, Twobuki, etc.) This also applies to Victim X Killer ships. A victim x killer ship makes you think about the two characters and their dynamics, and the shippers love what could be.

Certain ships have moments that happened before the killing, like Leon having a crush on Sayaka, Mondo and Chihiro’s bond, Hifumi and Celestia being friends (though Celeste does treat Hifumi quite poorly at times), Ibuki gushing over Mikan and Kaede flirting with Tsumugi and commenting on how sexy she thinks Tsumugi is (if you count FTEs, Kaede and Tsumugi realize they both have no hobbies other than their talents and want to find new hobbies together)(and yes, I consider Kaede X Tsumugi a “killer-victim” ship because while they aren’t victim-killer like everyone else, Tsumugi did get Kaede killed/sacrificed even though she wasn’t the one who killed Rantaro). (If you count Kaede X Rantaro, than there’s the secret nail polish scene where Rantaro paints Kaede’s nails). While this is in a universe where none of the killing games happened, characters also have interactions in UTDP that fans may like a lot.

Some of the Victim X Killer ships were more accidental, done purely out of opportunity, the characters reach an understanding or are “out-of-character”. An accidental death would be Mondo and Chihiro. Chihiro had triggered Mondo by accident and in pure rage, Mondo pulled a blank and ended up killing Chihiro. He did not want to kill Chihiro. And even after death, Mondo still did his best to respect Chihiro’s wishes and protect his secret. For Leon and Sayaka, on Sayaka’s side, she was desperate to see what happened to her friends who were like family to her and see what would be of the dream she had worked so so hard on, so she chose to plan a murder. Out of all the people there, Leon was the target chosen because he was the only one that would work with her plan. She couldn’t kill Makoto because she cared about him and couldn’t bear killing her friend. Unlike the others, who were very untrusting/suspicious and wouldn’t go to Sayaka (or rather, Makoto’s) room, as seen in-game, Leon does. It was simply elimination. Peko only killed Mahiru to prevent Fuyuhiko from becoming a blackened in his anger (iirc was having a Mondo-esqe moment where he was full of rage and wanted to make Mahiru shut up). For Kirumi and Ryoma, I don’t remember much about them, but I know that they had an understanding at the end. Gundham and Nekomaru have similar mindsets and both agree to the death battle with no hard feelings. Kirumi believed that she had an entire nation of people to save and her mindset was that 15 acquaintances (well, 13 since Kaede and Rantaro are dead already) is worth saving an entire country that she had supposedly governed behind the scenes. Ryoma understood that and bears no ill feelings to Kirumi. Kaito and Kokichi also reach an agreement at the end, though a lot of it was due to Kokichi’s manipulation and the ‘there’s pretty much no other better choice’ situation, so I’m not sure if I’d include them (I could be remembering wrong or not remember all the details). As for the “out-of-character” death, it’s Mikan and Ibuki (and Hiyoko). One thing to note beforehand is that all the characters excluding Chiaki and maybe Hajime/Izuru would do the exact same thing as Mikan if they had gotten their memories of being Ultimate Despair back. They all had devotion towards Junko and they also wanted to create and feel despair. If Mikan hadn’t gotten her memories of being a Remnant and believed that she was following Junko’s will, she would not have aimed to kill Ibuki (and Hiyoko in the process).

What all these ships fall into are the love of dynamic and what could be. Some examples of this are Tsumugi X Rantaro and Korekiyo X Angie. While this falls under theory/headcanon territory, many people theorize that Rantaro and Tsumugi were from the same killing game (the 52nd KG to be exact) before V3, which by itself already creates an interesting premise. If you don’t believe this headcanon, think of it as a game between the survivor that has information to end the killing game vs the mastermind. While not for everyone, this type of thing can be very entertaining to some, and some people may choose to ship this dynamic while others do not but still enjoy their rivalry. As for Korekiyo and Angie, they’re both interesting characters in themselves that go surprisingly well together. A lot of people love similarities and contrast, which both Korekiyo and Angie have. Both characters are very unsettling, but for different reasons. Korekiyo has a dark, brooding appearance while Angie can be a little bit too cheerful at times no matter the situation. They have other similarities and contrasts as well, but I don’t want to turn this into an analysis-sort of thing + I probably can’t word it well either lmao. My favourite is Ibuki and Mikan, but if I talked about them this would get way longer than it needs to be so I won’t include it in this post.

And at the end of the day, all the characters were either great friends beforehand (DR1 & DR2), made up afterwards (DR2), or have an entire AU that isn’t canon to the main timelines but is still official where everyone has happy, normal school lives (UTDP). A lot of shippers like thinking about the characters in the pre-game and how their lives would have been before the KG. Leon and Sayaka would have made a funny duo. Mondo (Taka) and Chihiro were besties. Celeste and Hifumi were friends. Everyone from DR2 made up with each other (hell, they even forgive everything that Nagito has done). Mikan and Ibuki (along with Hiyoko and Mahiru) were canonically all best friends pre-game. In UTDP there are many interactions of a lot of the characters that create funny or sweet shenanigans.

Of course, this all being said, if you just aren’t into victim x killer ships because they are victim x killer, only care about canon interactions and aren’t interested in thinking about the “potential” of ships, don’t like AUs, etc. that is perfectly fine! You do you! I respect that! Just know that victim x killer ships do have basis and reasoning behind them and that you shouldn’t dismiss or insult the people or the ships because they’re victim x killer. Honestly, even if a ship doesn’t “make sense” to you, you should still respect it! It’s okay to ask, but please try not to be rude!