A lonely older man who has lived his whole life avoiding others, finds himself in contact with a mysterious creature from the sea whom he communicates with in a black seaweed notebook. He starts becoming more and more open with others with this new relationship, falling more and more in love with Akiho (the sea creature) as time goes by. Ultimately, he gets torn between his love for Akiho (gender neutral) and for the new blossoming relationships he has with other people, and has to decide where his affections truly lie.