Remove strings and slice celery as thin as you can, and sprinkle with 1/4 tsp salt. Let it sit for 5 minutes.

Cut the end of chili pepper, remove seeds out, and slice thinly.

In a bowl, whisk rice vinegar, sugar, and salt together until the sugar dissolves. Squeeze water out from celery, and add to the vinegar mixture. Then add sesame seeds and chili. Chill for 30 minutes.