Sugar + Spice! Ano Ko no Suteki na Nani mo Kamo

The main character (Araki Kazuma) is a high school student. But, he has lost all his memories due to a traffic accident. He doesn’t remember anything. All he knows is his Japanese, which at least allows him to speak with the person in front of him, who claims that he is suffering from a strange variation of amnesia, where his basic survival knowledge is kept intact, but his memories are sealed away by a trauma as if he didn’t want to remember it.
Sending him back to the waiting room shows that a person named Aya calls him Ma-kun and tells him about his past, like the fact that his name is Kazuma, and his parents are overseas studying architecture.