Looking For Yaoi Manga

Hi I was recently reading this yaoi Manga but forgot to add it to my lists
So I try to describe it as accurate as I can

The main character works for a company and on a business "party" he accidentally peeks on a very popular and successful business man beeing involved in sexual activities with several other business men.
They meet again and the successful guy knows that the main saw him and makes a contract for his company in exchange for sex
They start a sexual relationship and become business partners basically

Sorry If it's a bit mixed up but it's a quite popular manga so maybe you know it

Hi can someone help me figure out this manga about poor uke x rich seme. They known each other since elementary school. The seme was awkward and always ask insensitive ques to uke. He would share his toys with classmates. They reunite again and seme trying to help uke settle the debt. Uke gradually fallin for seme but got angry cause seme tryin to use money to make uke fall for him. I cant remember if this manga oneshot or substory. Thanks..

I read it within the past year. It's about a teacher who gets assigned to this school with supernatural students. There's one student who bites or kisses the teacher and that 'marks' him. The student disappears because he's turning into this demonic creature.

It's similar to this manga:
http://www.mangago.me/read-manga/sensei_kowai_hanashi_shimasenka/