Charon Siphon

After high-schooler Nanatsu Io is crushed by disappointment in love, she finds herself pulled into a strange cafe, "Cafe Acheron," by pretty male workers, Kiba and Resato. Io decides to change herself by getting a job there as a waitress. In order to do so, she makes a contract with the cafe owner, Kiba, who tells her she must keep her stuffed bear (now conscious and referring to itself as "Father") with her.

(Source: MangaHelpers)