Using resurrection magic is a taboo in their world. Shao is aware that breaking the taboo would brand him as an evil mage smth like that. Perhaps my choice of words is not very good
Ok, another crazy theory... Ibuki is Luca, but broght back through the use of a forbiden spell by that Rose gal who is actually his mother (or maybe she's just building an "undead" army since he mentioned a garden before).