Ultraman S35E20 - Night of Insects Chirping

Teruaki rushes back to his parents' home when he hears that his father has fallen ill. However, this turns out to be a lie just to get Teruaki back home. Teruaki's father wants Teruaki to quit the GGF and the divide between him and Teruaki grows further. This is when they hear strange chirping from insects.

Apparently, the quality of the soil in the fields has changed over the past month and the crops are dying. As Teruaki and his father go around, they find a strange cave in the mountains...