Takumi Sakiyama, a supporting character in Pure Mail media, is Eri Aoba's ex-boyfriend. Their relationship began after his persistent pursuit led her to agree to date him. Sakiyama's true interest, however, lay not in Eri but in establishing a connection with her delinquent older brother, Hideo Aoba. This motivation drove his actions throughout their relationship.

Within the visual novel, Eri discovers Sakiyama's deception, realizing he used her solely to gain favor with her brother. This revelation positions Sakiyama as an antagonistic figure in Eri's storyline.

The OVA adaptation follows a similar path. After Eri briefly pretends to date Kei Ogata to deter Sakiyama, she abandons the ruse upon seeing Kei's discomfort around Midori. Eri and Sakiyama subsequently enter an intimate relationship. Their story concludes with both appearing together at PureBurger alongside the Ogata siblings.