LET ME INNNNNN ;)))))

This yaoi is one of the first ones that I read so the description may be a tad bit lacking but I will do the best I can...
It starts off with a young boy meeting an older guy in an abandoned building (I think) the older guy tells the young boy that he is either a scientist or an inventor... I can't remember what one it is exactly. It turns out that the young boy is from a rich family so either he or his father buy the abandoned building and turn it into a research facility and the young boy hires the scientist/inventor. The scientist/inventor makes some machine that will cause things to age quicker (I think this is what it was made for) - the young boy trips and falls into it and he is transformed into a young adult. During this time he confesses to the scientist and I think he kisses him? The effects of the machine only last for a little bit and then the young boy turns back into his original state. When the young boy grows up they have sex I believe.....

This is all I can remember about it because it has been so long. I am sorry if the description is vague...