*Title is originally in English, uncapitalized words are on purpose
Nakatani Taku attended the same junior high school as Hiwa Arina. So he said.
I was aware of one person who knew Hiwa Arina. And that was a third year, Mine Aki-senpai. When Arina and I were helping out the art club, Aki-senpai appeared as I was trying to figure out what to buy from a vending machine. It turned out that Aki-senpai was from the same junior high school as Arina.
I remember the conversation we had at that vending machine. If I recall correctly, Aki-senpai said that she and Arina were close. In other words, Taku fell in love with the Arina from junior high?
Hiwa Arina has two personalities.
This was the shocking fact that I had recently learned.
According to Akakusa-sensei, she had already developed her second personality when she entered high school. That was her main personality, the venomous-tongued Arina. And it was the Arina I know. The original personality of Hiwa Arina, who was born and given the name Arina, is the one I don't know.
The original Arina was probably the Hiwa Arina that Taku and Aki-senpai knew so well.
"Taku, have you talked to Arina since entering high school?"
"I haven't. I only recently learned that Arina-senpai went to this high school."
In other words, Taku was unaware of the bad-mouthed Arina.
In Taku's mind, Arina was still the same gentle Arina. Eventually, he'll find out. That's when he'll have to face a painful reality.
When finding out that the person he likes has suddenly changed, his instincts will naturally try and resist. Even if he tries to reason with her, even if he tries to treat her as he always has.
This was a problem of self-identity.
What are the parts that make Hiwa Arina Hiwa Arina?
Having a cat that looks exactly like a dead cat you once loved would never be able to replace your beloved cat. The heart will scream that it wasn't the one, even if you don't understand it.
Taku will suffer as well.
If I would dare to give him any advice, I'd say this:
「The Arina you know doesn't exist right now.」
Even if I told Nakatani Taku that right now, his feelings wouldn't waver. He won't accept it until he sees her in person.
But it would be unnatural if I refused to be the bridge that connected him and Arina. It would look like I was trying to prevent Taku from confessing. However, Taku's reality is tough. I felt sorry for him.
"Do you want to see Arina?"
"Eh?! Yes please! Wa~, I haven't spoken to her since I was a first year, I'm so nervous!"
"Hm? You didn't talk to her second year?"
"I couldn't. I moved at the end of my first year."
I see.
So the venomous-tongued Arina didn't exist when she was still version JC2. That meant that Arina, the venomous one, developed between the spring she entered her third year of junior high and her graduation. [1]
As Arina entered her third year of junior high, at the same time, Aki-senpai graduated and Taku transferred to another school. Taku and Aki-senpai only knew the original Arina.
What happened during her last year of junior high?
"Alright, let's see if you can meet up with Arina for the first time in a while. Give me some time to set it up. I'll set a place for you tomorrow or the day after."
"Thank you! Thank you so much!"
"Whoa, whoa, whoa. Leave it to me. I'll get back to you soon."
Taku bowed and went back to practice.
I told him to leave it to me. Now, then. What should I do?
When I got home, I asked my sister.
"Hey, Imouto. Remember Arina? The one who looked like she grew up in Antarctica."
"I remember."
"My kouhai wants to confess to her, but the Arina he knows and the Arina now are entirely different. Would it still be okay to let him confess without telling him that?"
"Sorry, I don't get it."
"Suppose there's a piece of chocolate on the table. It looks like the famous and tasty chocolate, but it tastes super spicy.
Now there's a fat guy dying to eat chocolate. And now, that guy is trying to grab that super spicy one. Should I overlook it, or should I stop him and make him misunderstand that I want to monopolize the chocolate. Which would you choose?"
"In that case, why don't you stop him? That's cute."
"I guess. What if we go back to Arina's story and think about it in that situation?"
"Do you simply mean whether or not you should stop people from trying to confess to Arina?"
"I'm leaving out the small details, but that's the gist of it. What do you think?"
Hmm. Ugin tilted her head.
"Let him confess. It's bad to mess with someone else's love life, Ani[2]."
"That was an oddly convincing way of putting it."
"For people who are trying to confess, stopping it will just make their feelings boil."
"I think he'd make a good stew."
"You should help him anyway. You may not get it, Nii-chan, but not being able to express your feelings will have a pretty big impact on you for the rest of your life."
"I understand. I'll save this for reference."
"Love is all you need[3]. Let's get this off your chest, Nii-chan."
"I'll get a tattoo."
My sister had some good advice. I knew it was a good idea to talk to her about it.
Now I just need to talk to Arina.
[1] When Sui says 'version JC2' the JC2 is an abbreviation for 'joshi chuugaku ninensei', meaning 2nd year junior high school girl. 'Joshi chuugaku' means junior high girl and 'ninensei' means second year. This is similar to the abbreviation JK, which stands for 'joshikousei' and is more commonly known (amongst weebs, yeah, that's right, I'm calling you out). The school year in Japan begins in the spring, more specifically April, and students graduate junior high their third year. So here Sui is essentially saying that the venomous tongued personality developed during Arina's third and final year of junior high.
TLDR: 'JC2' stands for second year junior high girl, Sui is saying that her venomous tongued personality didn't develop until her third and final year of junior high
Sorry if you read through this and it bored you 
[2] 'Ani' is another way of referring to an older brother
[3] In the raws, she said this in English