This was the best onsen I went to in Japan, and it's included with the hotel. They have a BEAUTIFUL indoor and outdoor hot bath, as well as a hot sauna and cold bath. I went to 5 different onsens and this was the best, it was a great way to spend the last few evenings in Japan. HOWEVER, be warned: no tattoos allowed (most other onsens this wasn't an issue, and thankfully I have none anyway).
The hotel is walking distance to Nagarekawa, which is a lovely and popular neighbourhood for night time restaurants and izakayas. Quick bus ride away from the other tourist attractions like the Peace park/museum, and a short bus ride from Hiroshima Station. Pillows were a little hard, but I still slept great. I would recommend this hotel to everyone.