Before heading for the hot springs, you get to choose which Yukata to wear. The ladies get more choices.
Once you pick up your yukata, you head to the mens or womens onsen. You must remove all your clothing before entering - if you are shy about other people looking at your dolphin or eyes then you probably should avoid. Do bear in mind that you occasionally bump into others who may take a fancy to you and stare at your dolphin or eyes...
Males who physically bump into another person inside the onsen by accident may need to disinfect their dolphin afterwards. If you want to avoid being bumped into, just walk along the wall with your back facing it.
Mixed onsen hot springs are known as Konyoku [混浴[こんよく]]and you can see some examples at Google. The image of Konyoku however is that of elderly ladies with long saggy eyes but lately, there seems to be more young girls don't seem to mind sharing while wearing nothing but a soft n tender birthday suit.
This may sound like heaven to some but there were some men on 2 channel who complained about nekkid girls getting in the same hot spring as them.
How about you? Are you fine with others of the same gender seeing your lil bro or oppai? Would you be fine in getting into a mixed Konyoku where the other gender can see your yummies?