I stayed here for 2 nights and I absolutely loved the ocean view from both the room as well as from the terrace.

It's also right next to the beach so you can walk out the back door to a semi-private beach.
There's a marine shop next door if you want to try marine sports - I did Stand Up Paddle.

About:

Fairfield by Marriott Kagoshima Sakurajima is a charming hotel nestled in Kagoshima, Japan, offering a relaxing escape with stunning views of Sakurajima and Kaimondake. Guests can unwind in cozy rooms equipped with free Wi-Fi, shower booths, and 49-inch flat-screen TVs. The hotel is conveniently located near Michi-no-Eki Tarumizu Hamabira, providing easy access to local dining options and attractions.