Ico

From Wikipedia:

Ico is a 2001 action-adventure game developed by Japan Studio and Team Ico and published by Sony Computer Entertainment for the PlayStation 2. It was designed and directed by Fumito Ueda, who wanted to create a minimalist game around a “boy meets girl” concept. Originally planned for the PlayStation, Ico took approximately four years to develop. The team employed a “subtracting design” approach to reduce elements of gameplay that interfered with the game’s setting and story in order to create a high level of immersion.