Negi only took advantage of Rakan because Rakan wasn't being serious for much of it and because they were pretty friendly.
I'm betting Chao's history results from a reality merge on Mars.
I'd really like to see Rakan feed Fate through a meat grinder while Negi enjoys the party without even notice it's happening. Don't expect it, but it would be nice. I don't want to read a long fight sequence here.