Chika is deluded, hard.
That is the only thing I can't really understand about her transition from a mere human to a Shiga. It's the power high of a lifetime and a heavy dose of coke is cough medicine for children in comparison, but expecting Hirota to be a loyal companion after putting him through so much shit is just foolish.
Then again, too much power all at once can make anyone weird in the head.
Also, poor Souichi. Did anything ever go well for this poor bastard in his life?