"We couldn't raise prices, so we decided to replace ingredients." That is how a spokesperson for Kiyoken Co., a food company based in Yokohama, described the situation. The company partially changed the side dishes in its "Yokohama fried rice" bento on June 1. The meal sells for 890 yen (about $5.60), including tax. The bento, popular among women and children, contains small portions of side dishes including shumai dumplings, simmered bamboo shoots and other items. But after chicken prices surged, Kiyoken replaced one of its most popular side dishes -- chicken in chili sauce -- with shrimp in chili sauce. It was the first menu revision in about 20 years. Kiyoken had been using imported chicken from countries including Thailand. But "around March, when the situation in the Middle East worsened, we started seeing chicken prices rise," the spokesperson said. The company had already raised prices for all of its bento products in February. Seeking to avoid further price hikes, it opted to change the ingredients instead.