[Kimono/Yukata Dressing: Basics] Collar Alignment
The collars of traditional Japanese clothing are always stacked with the left collar on top, regardless of gender.
To put it simply, it means that you can insert your right hand into the chest area. During the tea ceremony, you insert the kaishi paper (paper towel) on which sweets are placed into the chest with your right hand, but you can't do this unless the left collar is up.
If there is no one around or you feel uneasy, make sure you can put your right hand in!