The arc/world fragment in which this takes place is Beyond Midnight, a manga-only arc that basically details, at least in part, the bad end of Atonement –one where Rena ACTUALLY blows up the school and everyone inside, including her, dies. The arc only mentions that in passing, however, being far more focused on an adult Shion's adventures in trying to get one up on the rival faction of her family's yakuza organization while several tourists are entangled in her/their shenanigans.

June 28th, 2021

It was later –some time after she gave the rest of Mifune's faction her appreciation for what they had done to her mother– that Shion came back to Hinamizawa.

The ghostly village was the same as it ever was: abandoned by everyone, not a soul in sight, living or dead. It was just her and Kasai in the car –maybe a foolish lack of security for the one who was the head of the Sonozaki family, now, but after the deeds she had done here last time, she had a feeling that nobody would attack.

Besides, it was Watanagashi.

The wind stirred her hair gently as she stepped out of the car, moving with purpose but no haste towards the school. Such economical, powerful strides were part and parcel of becoming the Sonozaki Head, leader of a yakuza group and other bits and pieces that were now so much less with the destruction of Hinamizawa.

As ever, something desolate tugged at her heart as she saw the splintered and blackened posts –the fact that only single a jagged and wavering wall of the first story remained, barely a meter high, and everything else was a skeleton. The entire school had degenerated into an ashen husk, so that you couldn't even tell what it had been meant to be as a whole building.

The Tamahajiki no Katana was still there, pierced into the earth and looking much the worse for wear for being left outdoors for so long. Shion grinned briefly at the thought of the shrill lectures her deceased family would bestow upon her if they knew how badly she was treating the ancestral weapon –heir to the Sonozaki line she may be, but she really didn't care much more for her heritage now than she had when she proclaimed her love for Satoshi-kun in the torture basement and gotten three fingernails ripped off as a punishment, all those years ago.

Satoshi-kun…

Kasai remained a respectful distance away, by the car, as Shion reached the ancient sword, stabbed into the dirt just before the ruins of the school, like a memorial tablet.

"I used to hate you, you know?" she said aloud, not looking up from the tarnished blade. "I used to lay awake at night, cursing you, wondering if there was some way I could get revenge for what you did. If you'd left remains behind, I'd have probably done something unforgiveable to them."

The world around her was silent, because of course it was. Ghosts or no, it was still only her and Kasai in the village now. Shion took a deep breath and looked up, staring at the ruins of the school. Even after so many years, the smell of gasoline leaked from it, poisoning the air with the subtle tang of mankind. It was the same kind of smell you got at every gas station, and it was an unseemly blot in this otherwise natural vista.

"Maybe it was cruel of me." she admitted, tucking a strand of hair behind her ear as the wind blew again. "You died too, didn't you? It wasn't like you set the bomb and walked away. You were right there with all your hostages, until the very end. I don't know if I should loathe you or respect you for that."

No one responded, not even Kasai.

"I don't really talk about it, you know?" Shion said. "Not to anyone. They'd all say the same thing, that at least it was a quick death, at least they didn't choke on gas like everyone else. But damn –you know that they'd have managed to survive, Rena, you know that!"

Alone in Hinamizawa, Shion let the tears come as she shouted at the ruins.

"Onee and her club –they were invincible! They wouldn't have died because of some stupid gas! Why didn't you ask your friends for help, instead of killing them?! Why…?"

She collapsed to her knees, digging her fingers into the dirt as it curled under her fingers, bitter and blackened even after all these years.

"Why…?"

Why did you have to take everything from me?

Why did you have to leave me all alone?

Why couldn't I have died alongside you?

Why do I have to be alone?

"Why…?"

Shion wasn't embarrassed to cry, but here in Hinamizawa, in the village of the dead –this was the only place she felt safe enough to cry, and even then, it was when she didn't have any company, didn't have that boy Otobe standing over her shoulder and looking so damned like Satoshi that her heart broke.

So here, alone, now, she cried until her tears ran out, watering the charred earth with her grief, until she felt marginally better.

"Sorry for that." Shion snuffled, managing to lift her arm up and wipe it across her face. "I didn't actually come here to yell at you –I just…kinda needed to get that off my chest."

She stood up again, swaying a little as her cramped knees protested. She had been in one position for far too long. She dusted off her legs, turning to pick the sword up and slide it back into the sheath she'd brought along for this exact purpose, before tucking that into her obi.

"Anyways, what I really came for was to apologize." she said, a hesitant smile creeping over her face. "I –I did hate you, for a while, but I guess…I'll never know the truth, huh? What made Rena act like that, what drove you to kill your friends…"

"I'd like to know, too."

In any other situation, Shion might've jolted back, might've grabbed for the sword she'd just recovered or the pistol on her hip, but she knew this wistful voice, and she'd heard this kind of thin, ghostly whisper before. So she watched with calm eyes as a wisp of something like mist congealed before her, fighting against the dying sunlight cast by the sun sinking low over the western horizon. Shion had been here longer than she'd thought –she'd have to hurry to have a proper Watanagashi and make it back to her hotel before the bodyguards there began to worry.

The wisp of something not-entirely-there formed a girl in a white dress and white cap, a young girl just on the cusp of high school. Her blue eyes were deep as the night sky, and unfathomably sad.

"Why did I believe such ridiculous stories…and do such foolish things? I don't know either." Rena said, her whispery voice lost, sorrowful. "It felt as if I were living inside a dream…a nightmare. Everyone was against me, everyone was trying to hurt me. But that wasn't true, was it?"

"It wasn't." Shion managed. "I- I don't know what was happening to you either, Rena, but I know Onee and the others would have never left you behind. They would've helped you."

"I know." Rena said, and the lament, the regret in her voice was so deep that Shion would've started crying all over again if she had any tears left. Rena was crying, even as a spirit, as she looked at Shion across the void that separated the living and the dead. "I'm sorry for killing them, Shion. I'm sorry for taking them all away. I'm sorry for not believing in everyone."

"I'm sorry for not believing in you." Shion choked. "I'm sorry for hating you all those years."

She ruthlessly pulled on a shaky smile, a skill she had mastered long ago –to smile brightly even when her heart was breaking– as she brought two fluffy balls of cotton out from behind her back.

"Would you like to wash away those sins with me?" she asked as Rena's spirit smiled through her tears. "It is Watanagashi, after all, and the river's not that far away at all by car."

"I can't ride in a car, Shi-chan."

"So I'll toss your ball in for you, or you'll show up on the other side of the river to do it yourself?" Shion asked, and Rena laughed brokenly, wiping her own tears away with the back of her wrist.

"The river, I suppose. Thank you for bringing the cotton, Shi-chan."

"Well, I have responsibilities now." Shion said, her eyes falling to the two little balls of fluff, her smile fading a little. "I'm used to coming prepared."

9.40 AM, USA Central Time