double grave of lovers who died together
A grave or memorial for a pair of lovers who died together, often by suicide. The name evokes the image of a pair of birds flying wing to wing.
That temple has a famous double grave of lovers who died together.
From 比翼 (hiyoku, 'wing to wing') + 塚 (tsuka, 'mound, grave'). The term is associated with the image of a pair of birds flying together, symbolizing inseparable lovers.