Lagoon Lounge : The Poisonous Fountain

This is the story of young man who lived and worked in the city, but quit due to a decline in his health and is invited by his childhood friend Sousuke to live with him and recover.
He lives in a small village nestled beside a lagoon.
Around the same time, a strange phenomenon has been occuring there.
On the weekends, there are large earthquakes and what sounds like the stomping of giant.
What could be causing those earthquakes and stomps!?
The protagonist gradually uncovers the secret behind them as he spends time with the residents of village.