Let This Grieving Soul Retire, Vol. 8 (manga)

All their blood, sweat, and tears...They've spilled a bit more than the rest of you.The capital is in a clamor as word spreads about the arrival of a band of high-level hunters-including Arnold Hail, the infamous Dragon Slayer known as the Crashing Lightning! Krai, of course, couldn't care less about anything other than the upcoming Zebrudian auction, but he'll be in trouble soon if he doesn't get his relics charged fast. Thankfully, Sitri has devised a "top-secret training method" that can both charge the relics and boost the whole party's mana reserves...just in time for a pair of superhuman Noble Spirits who have a bone to pick with the Grievers!