This was such a cop out chapter that was rushed to oblivion so that Kurono x Reika fans would be satisfied. That's why the real Kei is so out of character, because the mangaka clearly didn't give a crap about this chapter and just wanted to get it over with.
I'm honestly pretty pissed about this. This manga is so great yet at the same time, there are chapters like this that have no care put into them whatsoever. It's so half-assed.