Car Day trip to beach

Hi All,
I am looking for some recommendations for a fun drive around 3 hours from Kanagawa/Tokyo.

The Obon holidays start tomorrow and I have rental car booked for the weekend from 13.30 to 1:30 (after midnight next day) to avoid traffic.

I want to visit some beach and just chill by myself (read a book, eat snacks) and come back. Just wanna escape the city life.

Let me know your thoughts/advice.
This will be my first solo drive trip of this type.

Thanks in advance.