Considering hentai logic, I originally thought she was going to start sniffing something and masturbating, but I guess not.
Great ending though. He seemed like a bit of a jerk at first, but at least he actually kept his word. He said he'd thinl about it, but was a decent enough person to actually do what she asked for. Also, she's such a nice person that is willing to put her body on the line just so that he would continue to run, which is ostensibly his passion until something happened, and she just wanted him to succeed at what he is passionate about, I guess.
I think she'd make a good wife. He should probably just marry her, and they can practice sprinting together.