Text and picture copied from "Japanese Infantry Weapons" cincpac cincpoa Bulletin 55-45, 15 March 1945 :

"The One Half Kilogram Incendiary grenade is 50 mm in diameter, approximately 5½ inches in length and weighs about one pound. It may be thrown by hand or projected from a Type 89 50 mm grenade discharger.

The percussion fuse is the same as those employed in the Types 91 and 97 hand grenades. The body has an unpainted brass cover and contains an explosive charge of about ½ ounce of picric acid and an incendiary filling of 4 ounces of white phosphorous.

There is an 8 second delay fuse".

Photo thanks to Dr. Ruby