Karasuma Reiyu actually quite liked his little junior, even if he occasionally had to teach Tanjirou the true value of life in the harshest way possible.
Still, seeing Tanjirou genuinely grieve over the death of Hand Demon didn't make Reiyu think he was being fake. His junior was, quite literally, kind to his core. After all, the day before Urokodaki Sakonji had brought him back from training, Tanjirou had spent an entire night agonizing over whether to kill a demon. In the end, the sunlight did the work for him, burning it to ash—and it was the first time he realized demons feared the sun.
Watching Reiyu's face, twisted into one of his trademark smirks, Tanjirou spoke softly:
"Yeah… I don't know why, but I just feel sorry for him."
He glanced at Reiyu and a small smile appeared on his face.
"You know, Reiyu-senpai… I think you're kind of like me. You just hide it to maintain your image. Otherwise… you'd probably scold me—or hit me a couple of times."
"Hmm, maybe… but I just think they're a little pitiful. That doesn't change my resolve to finish them off," Reiyu said, scratching his nose awkwardly, realizing that Tanjirou had already caught on to his thoughts.
Then he suddenly remembered Urokodaki Sakonji's instructions before he left Sagiri Mountain to participate in the final selection.
"Oh right, Tanjirou. The old man said that if I met you on Fujikasane Mountain, I should stick with you and protect you for seven days. So… from now on, your senpai is going to take you along, show you how to look cool, and let you fly."
"Alright! Having you around, Reiyu-senpai, makes me feel much safer," Tanjirou said with a nod. Though Reiyu liked to hit him, having him as a protector definitely increased his chances of surviving the final selection.
"By the way, Reiyu-senpai… Master told me to remind you not to always act so cocky and self-important. He also said to be more modest… or else you'll never get a girlfriend."
Tanjirou's face remained full of his innocent smile, completely unaware that he might have said the wrong thing.
Reiyu froze for a moment, then a mischievous, almost sinister grin spread across his face.
"My good junior… Master's advice is sound. Since you've been so obedient, I guess I'll… train you. Boost your body's resilience."
"Uh… thanks, senpai? Train me? Boost my… resilience?"
Tanjirou's eyes snapped open, just as a fist roughly the size of a sandbag appeared directly in front of him.
"Ahhh!"
The forest rang with Tanjirou's agonized screams.
"Senpai… aren't you going a bit too hard this time? I don't mind getting hit, but if you need me later, I might be too hurt to fight!"
Tanjirou, his face covered in bruises and swelling from Reiyu's hits, clutched his aching waist and stumbled along behind him.
Ahead, Reiyu walked casually, hands clasped behind his back, eyes scanning the surroundings, utterly nonchalant.
"My foolish Odododo… just how dumb are you? You actually thought I'd need your help? Huh? If I ran into an opponent that needed backup, you really think you could handle it?"
Reiyu glanced at Tanjirou, whose face now resembled a pig after Reiyu's assault, and adopted the tone of a strict mentor teaching his child.
"I get it, senpai… but next time, could you hit me a little lighter? And… why don't you ever hit my forehead?"
Strangely, despite Reiyu's habit of hitting him, he never struck Tanjirou's forehead. Even if Tanjirou purposely presented it, Reiyu would deliberately aim elsewhere.
Reiyu's lips twitched. He remembered the first time he'd hit Tanjirou's forehead during training. Even with minimal force, the blow had caused a minor fracture in his left hand, taking three full months to heal. Luckily, it wasn't his sword hand. Ever since, Reiyu made sure to avoid the forehead.
Hearing Tanjirou ask this, Reiyu's mind flashed back to that fractured hand, fueling a mixture of amusement and irritation. Smiling broadly, he approached his junior once more.
And then… Tanjirou's shrieks echoed through the forest again.
After venting, Tanjirou was sprawled on the ground, barely able to rise. Reiyu often left him in this state, but given the special circumstances, Tanjirou quietly held a tiny grudge—though he dared not voice it.
Dragging his half-dead junior, Reiyu found a safe spot on the mountain for Tanjirou to recover.
Perhaps foreseeing Reiyu's brutal tendency, Urokodaki had already prepared healing ointments before their departure. Reiyu applied the salve to every wound, then ignored Tanjirou, lying down himself to rest in the sunlight. After more than a day and night without sleep, even someone like Reiyu needed a break.
Meanwhile, Tanjirou, in too much pain to sleep, assumed the role of watchman. Any anomaly in the surroundings, and he would immediately wake Reiyu. With his superior sense of smell—better than Reiyu's Mangekyō Sharingan for detecting threats—Tanjirou was perfectly suited for the role.
Sitting against a massive boulder, Tanjirou's mind harbored a mix of complaint and admiration. Sure, Reiyu had beaten him to a pulp—but his feelings were more fondness than resentment. He couldn't bring himself to truly dislike his senpai.
"Honestly… Reiyu-senpai's really good to me… it'd just be perfect if he didn't hit me," Tanjirou muttered with a tired smile. Exhaustion soon overcame him, and his eyes closed.