[Balzac]

Spoiler for Saya's Ending:

My interpretation for that part was this, the endless game has to go on, i.e. the world has to continue its function in helping Rin and Riki to become independent (I assume you already know the details of Refrain). Saya was an unknown, unprecedented variable in the whole process, much like Doruji to a lesser extent, and Kyousuke might have felt that there was a slight chance that Riki would be distracted from the ultimate goal, nice guy that he is, if he continues to spend time with Saya. So he "devises" a machine to use as bait for Saya so that presumably she would be free/kicked out of the world. My memory is hazy, but that last confrontation has him basically "kill yourself" so she can be removed from the world.

Now here's where interpretations vary as to how she ended up after leaving the world - did she die in that accident in the real world, was she saved, etc., feel free to pick whichever interpretation suits you. Within the artificial world, events are free to continue and culminate in Refrain. Riki and Saya may or may not have reunited in the future, inviting her to the Little Busters! as with the other heroines... I ascribe to the good ending, because that's what I prefer.

And Doruji's awesome for racking up skills, as I recall.