Konaki („crying“) Sumo or Nakizumo ("sumo of tears") is more than 400 years old tradition organized in some Japanese temples. Konaki Sumo organized every April in the Sensoji Temple in Tokyo includes almost 100 babies.

Other locations with Konaki Sumo contests are Ikiko shrine in Kanuma-ski, Tochigi (contest in September); Yamajioji temple in Shimotsu-cho, Wakayama (contest in October); and at Saikyoji temple, Hirado (contest in February).

Two Sumo wrestlers, each holding a baby, face each other and wait whose baby is going to cry first.

There is also a priest who shouts and waves at the babies.
If both babies start crying at the same time the winner is the one who cries louder.

There is a Japanese proverb that "naku ko wa sodatsu" or "crying babies grow fast". It's believed that louder that baby cries the more gods' blessing it gets.

Japanese have another proverb which suggests the opposite. Japanese say that "neru ko wa sodatsu" or "children who sleep grow fast".

Apart of yelling and crying, Konaki is also a time of praying for baby's health.