Oh Yuusha yo, Itte Shimau to wa Nasakenai! [Japanese]

The hero Yushia and his party headed towards the demon lord’s castle to defeat him, but he fell into the demon lord’s sub-commander’s trap and was turned into a weak level 1 shota. When he reunited with his party members, he earnestly asked for their help in training him back up to regain his lost powers. But each of them wanted him for themselves and took full advantage of his unfortunate situation to make him their playtoy. Will he be able to endure their ecchi training? What will become of his quest to defeat the demon lord?