In order to strengthen defensive capability, small kuruwas, such as an obikuruwa and a koshikuruwa, were sometimes built around the major kuruwas, such as the honmaru.
防御力強化の目的で、本丸などの主要な曲輪の周りに帯曲輪（おびくるわ）や腰曲輪（こしくるわ）などの小曲輪を配置する事があった。