Wash the kabocha squash thoroughly, remove the skin, and cut into bite-sized pieces.
Place the kabocha squash in a steamer and steam for 15 minutes until cooked.
Put the cooked squash in a bowl, let it cool, and mash with a fork.
Finely chop the boiled eggs, cucumber, and onion.
Add yogurt, salt, and pepper, then mix all the ingredients together.
Place in a bowl to finish.