It's a big mindshift for real. My first experience was in my first year here. My co-workers and I went hiking and then we all went to the onsen afterwards. My plan was to avoid the onsen part because there was "no way I was going to get naked infront of my co-workers". You know when there's a beach trip in Jamaica, not everyone goes in the water. Some just hang out. Well, this was different. Onsen time was for everyone. Haha!! I got in and couldn't remember being so conscious about being naked. I was no way comfortable and had to get in my bath when I got home. My shoulders were stiff! Lol!
After a second onsen trip though, I realized it can could be a relaxing experience. Still not totally comfortable but once I get in and there aren't too many people, I can relax without much care. Still prefer to do it with just family.