In-game story:
It is the late 90s. You are an engineer with an undying love for the sea who surfs as a hobby. You work on your dream project, a fast, large, unsinkable ship to explore the waters. One day, tragedy strikes as a huge tsunami hits the city. As you seek protection under a tori gate, you find yourself teleported to a strange place. The wonder turns into horror as you realize that you are now in the afterlife along with every victim of the disaster... You eventually try to accept your fate and make peace with it.

Look out for details in the sound and environment, they tell a lot about the lore. The abstract visuals are meant to express the character's feelings. Also, look for a secret easter egg behind the mountain ;)