Six years ago, on the 18th of May.

The lingering feeling of spring, in contrast to the feeling of the current winter. Sana was right. Everything should be turned back in time, and this day should be scraped from all of our memories. Then nothing will be changed.

The morning

"We are going now. Thank you for the meal, Ms and Mr Kim." Nayeon said before she stepped out of Dahyun's home, "It was really delicious."

"Thank you, Nayeon," Ms Kim waved Nayeon goodbye and looked in the distance, only to see her daughter, waiting impatiently. Despite Dahyun's outgoing personality, the girl never liked to display it in front of her parents. From all the years Nayeon has been with Dahyun, she never saw Dahyun show any affection towards her parents.

It was somewhat ironic, as Dahyun was shy around her own parents.

"Please take care of Dahyun for today too." Mr Kim said while looking at Dahyun, "This kid will never settle down and behave for a bit. She must've caused enough trouble for you already."

"Oh yes, more than enough," Nayeon joked, which gained smiles from the two adults.

"I will see you tomorrow then. Have a good day." Nayeon bowed.

The afternoon

"Crap, is it Dahyun's birthday in 10 days?" Jeongyeon whispered.

"You don't know?" Sana turned her back to have a look at her friend. "How do you not know that!" The Japanese judged.

"I've been occupied by the principal lately, she's been asking me to clean up the school grounds for 2 weeks straight already!"

"Yoo Jeongyeon, Minatozaki Sana, both of you stand up."

Nayeon was about to warn her two friends to not talk in class, especially when the teacher was Mr Park, but it was too late.

Of course, the whole class focused their attention on the two.  Nayeon looked at them as well, Jeongyeon and Sana knew they were screwed. She then looked at Dahyun, who was sitting at the front, was showing a mischievous smile at her. Dahyun sat at the front row ever since she got called out for talking to everyone at the start of the year. At first, Mr Park demanded her to answer a maths question, which was way too hard for a grade 11 to solve. Even the smartest kid in the year stared blankly at on the board and shook his head.

It was the teacher's method of teaching, he used a student’s failure to embarrass him or her in front of the whole class.

Mr Park grinned at Dahyun as she walked up to the board to confront such a question. Dahyun took her maths notebook with her, and flipped through it desperately, and tried to search for clues. Mr Park continued the lesson while leaving Dahyun to work on the question.

It was deemed to be impossible to solve for a grade 11 student, but Dahyun solved it, although in 30 minutes.

Mr Park was undoubtedly shocked by Dahyun's ability, yet he still found a way to criticise her.

"You took too long." Nayeon recalled what her teacher said, "Y-You need to move in front to pay more attention in class."

Nayeon didn't know whether Dahyun just got lucky that day or finally used her brain for once, but the current scene where Dahyun smirking at the two of her friends was truly annoying.

It's not funny, Kim Dahyun! Nayeon gave the expression.

Jeongyeon and Sana sighed.

"I'll solve your stupid questions for them!" Dahyun shouted and stood up.

Oh my god.

Today's promise for taking care of Dahyun has broken already.

"Kim Dahyun!" Mr Park shouted.

Dahyun smiled at her teacher.

"Okay," Mr Park said, "Trying to play hero and save your friends hey?"<