My Virginity Was Taken at Age 30 by a Younger Man

From Pocket Comics:

"Let's be friends with benefits." She can't believe her first time was taken by a younger guy... Yukino Miyawaka is 30. She dreams of quitting her job and getting married, but instead, she finds herself at 30 without ever having had a boyfriend. Not able to handle her oppressive boss, she quits her job and that night, drinks until she blacks out. The next morning however, she wakes up to find herself in a hotel bed with an unknown man next to her. Then, that man, Kei Ootani, tells her something shocking!