Almost broke character there.

Edit: The ruby-character 'alternate pronunciation' thingy above was basically a typesetting trick to emphasize that onigiri was made from rice. This technique is used elsewhere where a kanji or some other native Japanese word is used to provide additional semantic framing/meaning to a sci-fi/fantasy/mythological term or loanword. It's kinda like using parentheses but without interrupting the flow of reading.

Though here it is inverted, with the base word being an English word ("Rice" in katakana) instead. This kind of use pops up every now and then when multi-language puns are involved.

The EN translation adapts this by writing "riceball" with rice emphasized in italics.