Nagi is a diver from a quiet fishing village where a series of strange incidents have been occurring recently. One day, a stranger takes her to an office where she is asked to recover sunken treasure at Kaijin Reef. Nagi agrees to do so, but during her dive, she gets exposed to strange radiation. Afterwards, she starts to experience spells where she exponentially grows in size. This causes a lot of problems for her and the people surrounding her.
Responding to the 5th screen grab:
This is the ideal female body. You may not like it but this is what peak performance looks like.