I'll Train You All Night Long -How Did I End Up As My Friend's Pet?-

Mahiru Iwasaki never expected to bump into her long-lost childhood friend, Shinya Konno, the very same day she was fired from her job and kicked out of her company housing. Due to her innate sense of justice, she'd confronted her overbearing and abusive boss by delivering a blow, quite literally.
Later that same evening, Shinya discovers Mahiru seated on a park bench, surrounded by her belongings with nowhere to go. Just when Mahiru thought her day couldn't get any more bizarre, she finds herself moved into Shinya's apartment under the most peculiar relationship title.