Disclaimer: I do not own Ghost Hunt; it is owned by Fuyumi Ohno. This is a work purely for entertainment purposes, not profit. (And fantastical ramblings about Naru are oh-so-entertaining.)
Obviously not set in the current time frame of the manga, but no spoilers.
Without warning the world tilted violently sideways. Pain exploded through Naru's head and dark spots danced in his vision. He could vaguely hear the commotion Mai, Lin, and the others made, but their shouts of alarm were drowned out by the vicious pounding of blood between his ears, muffling everything but the screaming pain. He had been attacked by any number of phenomena, but almost none of them had been so unpredictable or had slipped through his defenses so easily.
Slumped awkwardly against the chair he had landed against, Naru brought a hand to his already-purpling jaw and tested it gingerly. Slowly (oh, so slowly) his vision broadened again, and he was able to bring his eyes into focus on the man standing before him. Flushed and huffing, his usually banal expression contorted with a grim sort of smug satisfaction, Bou-san stared Naru down.
"There's more where that came from if you don't treat her well," he growled with menace, eyes flashing almost golden in his righteous ire.
Naru's eyes narrowed to dark, dangerous slits, but he didn't offer a reply. The two men faced off in a silently snarling confrontation. The air between them vibrated with testosterone-laden challenge until, finally, Naru lowered his gaze briefly to the woman beside him glaring indignantly at the monk and muttering dire threats of bodily harm. His expression softening almost imperceptibly, Naru finally nodded briefly at the older man. Payback could come later, and at his leisure. The thought made his lips twitch in anticipated satisfaction.
Mouth relaxing into a wide smile, Bou-san laughed and turned to gather a still-furious Mai into a bear hug.
"Congratulations, jou-cha—oof," he grunted as a not-so-delicate fist connected solidly with his solar plexus.
"Thanks," she replied with a sharp, Naru-esque smile. "I'll expect an expensive wedding gift."