I think Ruka does like the MC, he made her really happy knowing that he was pretty much filled with joy when she said she liked him the first time. Ruka likes MC because he really is a nice dude.
Before:
"I can offer you my pity, but my forgiveness? NEVER! Now prepare to be purged from the earth! Mowed down like grass... CRUSHED LIKE BUGS!!!"
After:
"I have made a severe and continuous lapse in my judgement"