This story is full of surprises and of course the the best prize is a surprise.
Riiko got a sex toy from the future on a website (boy how I wish it was real). She didn't return him on time so now she has to one million dollars (aka: the price for the perfect guy). The adventures they have together were all wonderful and all wasted because (here comes a spoiler) once they had sex Night , the sex toy, dies and the story ends. R.I.P. Night Tenjou.