Japanese-style soaking tub

Hi. I'm getting a bathroom put in with very little space. We thought we could only fit a toilet and sink. the ceiling slopes. I was thinking I could fit a Japanese style soaking tub where you sit in it. My friend in Japan says her one fills with the press of a button (so she doesn't need to remember to turn it off) and maintains a stable temperature. I'm wondering if anyone has found one of these and installed them. Please let me know