Genuinely why? This is some bullshitery, he wasn't special in our world, and he got isekai'd along with everybody else, but APPARENTLY the support is seemingly better at both offense and defense than all the other heroes combined. The setting is running an orphanage so he'd need to be good at a lot of things like maintenance/housework/etc., but combat¿ why?
If you really wanted action at least actually make him a support and have the others be combatants instead of giving him a Deus Ex Machina of a skill.
His skill doesn't even have that big of a disadvantage considering it's pretty generous at what it considers "protecting" as the girls weren't in imminent danger or anything they just HYPOTHETICALLY would be if MC doesn't stop the goblins, that's it, so what's the downside to his skill exactly¿