Koi To Karada No Kyoukaisen恋とカラダの境界線; Border of Love and Body; Love and Body's Borderline; Love Workshop

Right after he was dumped, Tarou got a call from his newly-wed older sister, asking him to babysit her husband's teenage son. Tarou arrived to find a disrespectful 17-year-old kid who seemed to hate his guts. How would Tarou cope with the situation?