On May 5th, Children’s Day, Kashiwa (Japanese emperor oak) mochi, a Japanese confection is especially eaten in eastern Japan. It is because a Kashiwa leaf symbolizes “prosperity of descendants”. There is usually “Koshian(こしあん)”, “Tsubuan(つぶあん)”, “Misoan(みそあん)” inside mochi.
Remember that you cannot eat a Kashiwa leaf.