AP/Dura: Kirumi upscales from 3.68 MJ, while Theory is 2.84 MJ. A roughly 1.3x AP advantage. Nothing game changing, though Kirumi does upscale from her AP value, though Theory can negate that AP disadvantage with his finishers, which he has 3 of.
LS: Theory is Peak Human. Kirumi is Athletic Human. Don't really need to say much other than this will be very detrimental for Kirumi to try and grapple with...a wrestler who has many years of experience in grappling/wrestling. For what it's worth, Kirumi can lift Theory's body weight, so maybe that could help her here.
Skill and Experience: Kirumi is surprisingly a lot more skilled than I initially thought. Though I still Theory holds the advantage here. Not only does he have actual on screen feats (which most of the Dangan verse lacks), but said on screen feats are more impressive than the skill feats Kirumi has demonstrated. Far from a skill stomp, but Theory does hold the edge in overall CQC. I will say that Theory's experience could be a detriment here, which I will explain a bit later.
Range: Kirumi holds a clear advantage here, having extended melee range with her Wooden Pole, and apparently dozens of meters with her guns(?). I'm wary about her guns, but since it's not listed on her standard equipment section, I think it's fine to restrict them and let her keep her Wooden Pole.
Stamina: Theory can last in a fight for extended amounts of time while taking shots from foreign objects like steel chairs, steel steps, and kendo sticks, which all leave many welts and bruises all over the wrestlers body. He can also fight through injuries such as broken fingers and a swollen/broken jaw. This is all very impressive, but I think Kirumi has him beat (though it's not by much). Being sliced/lacerated multiple times by circular saws while receiving piercing damage on her hands is a bit more impressive than what Theory has shown.
Others: Both individuals actually have a few abilities that they share. Both have Social Influencing, some solid Stamina/Pain Tolerance feats (Pain Tolerance needs to be added to Theory's profile), as well as Weapon Mastery. Though Theory's IR makes him harder to hit, along with that skill advantage. I'm inclined to believe that Theory takes this section.
Overall, I think I'll go with Theory high-diff, though Incon isn't necessarily out of the picture here. Theory is more skilled, but he has only 6 years of experience as a wrestler. While on this wiki, experience is a relatively niche thing, experience in WWE plays a huge factor in fights. There have been many times where a wrestler defeated their opponent via experience. Theory's still a rookie, and he makes rookie mistakes. A prime example is his arrogance, which can be a detriment here if he's not careful. Though I do think Theory's skill, as well as his IR, can somewhat make up for this gaping flaw. Also, Theory's fighting style is relatively simple. He's primarily a brawler, who uses stiff strikes and grapples to win his matches, though
he's deceivingly agile for someone his size. While Theory can pull out a flashy move here and there, his fighting style is still pretty simple, which makes it easier for Kirumi to avoid his attacks, despite being the lesser skilled of the two. Let's not forget Theory's finishers, and while I do think Kirumi can fight through getting hit by one finisher, she's not fighting through two of them.
TL;DR:
A-Town puts Kirumi Down!