Overpower
Isn't it Overload?
Yes, sorry, I mistyped that.
And as far as canon stuff in a fighting game goes, whenever Shiki is close to the enemy it's instant win due to his MEoDP. I'm sure canonically he doesn't need 300% of his Magic Circuit to cut anyone into 17 pieces.
If we went canonically, aside from the maids and Miyako, I would say Akiha would be the most in danger. Aside from Shiki, Ciel, Ryougi and Arc, Chaos would be unbeatable. God Form Ryougi would be god tier followed by Archetype Earth.
What are you talking about? 300% Magic Circuit is totally canon...when he just uses AD, he only cuts one line like he does in the VN against everyone but Arc. AAD or LA is reserved for the big players...300% Magic Circuit is serious business.
Still, aside from Aoko, the brief mention of Touko, Ryougi, and (possibly) Zelretch, there's still not much crossing over. They're definitely exceptions, not the rule.
Ahnenerbe, the cafe that Ryougi frequents is in the same town she lives in, thus why Azaka and Fujino are seen there after school in their uniforms. Ahnenerbe is also the cafe that Shiki takes Seo to in KT and it is also the cafe the girls have their meeting at in Plus+Period. There is mention that Shiki (Tohno) is not allowed typically to go there (4th wall) because of the possibility that he would run into Ryougi.
There is also the rule stating that only one set of MEoDP can exist at any given time. This is another point that people bring up to support KnK and Tsuki being different universes. However, Ryougi's eyes are not MEoDP but rather MEoO which far outclasses Shiki Tohno's eyes. They are of completely different class ratings as well on the magical spectrum.
It'd be kinda scary, if they did. How would Azaka know which person was the right one to be incestually smitten with? Then again, how would Akiha? And if they somehow got mixed up, would either of them speak up when their respective "sisters" cried out "Nii-san!!!"
While similar in appearance, I'm sure they would be able to tell the difference among one another. Everyone has a twin, or so the saying goes...but family can still tell the difference due to voice, mannerisms, etc etc. I don't think there would be an issue.