The Flow of Wearing The Female Yukata
7. Settle Ohashori with Koshihimo
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It should be easier for beginners to use the Koshi-himo again before tying the flat belt, Date-jime.
If you don't settle ohashori folds this way, you check 8. 
- Adjust the collars, hold them with your right hand, and wrap the Koshi-himo twice around the chest to secure the collar line.

- Entwine the ends tiwce.

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Cross them and tuck them under the Koshi-himo itself.
See 8. for another way to settle Ohashori folds.