[FOUND]"The Solitary Castle Rots" (Chapter 5)

I remember the beginning of the manga about a young man who need to earn more money and hold several part time jobs. One of his job is part time janitor at night in an office building. In the end he choose to work as sex worker because the job can earn more. He meet an older man who is a businessman or salary man. At first, they didn't have sex and basically just chatting. I think the older man is trying to experience love/sexual relationship between man. At the end of the day, the older man pay the young man for his service. They meet several times after that. As the relationship deepen, he falls in love with the older man and thinking to stop meeting with him because he doesn't want only his money.

The young man cut off all his contact with the older man and went back to work as a part time janitor. He resigned being a sex worker. At one night when he is working as janitor, the older man recognized him and their feeling become mutual. The young man is apparently have been working at the building where the older man is working.

As far as I know the younger man is working as part time janitor. Can anyone tell me the title of this yaoi manga? Thank you for your help!

In "The Solitary Castle Rots" (Chapter 5), the main character only fronts as a call-service worker and never actually accepts any payment, but I'm pretty sure it's the one you're describing.

@weird1
I remember the part where their feeling become mutual which left me a deep impression. I've been trying to find the manga and didn't remember it is one of the chapter or a whole manga series. I'm glad to find this manga now! Thank you so much for your help!

You're welcome! I really enjoyed that chapter (and the entire series), as well!