Lying to Mom (2018)

Koichi is a son in the Suzuki family. He is a hikikomori ("recluse") and dies suddenly. The rest of Suzuki family, father Yukio, mother Yuko and daughter Fumi, fall into confusion. Especially the mother Yuko, who is shocked by her son's death, and loses her memory. Fumi lies to her mother and tells her "Koichi stopped being a hikikomori and now works in Argentina."