Noon, Student Council office.
"Swap Devil Piecess?"
After hearing Tatsuma's surprising suggestion, Sona was unsurprisingly stunned for a moment.
A moment later, she pushed up her glasses and asked with some hesitation, "Does... Rias know about this?"
Tatsuma said, "She knows."
"She doesn't object?"
"She objected, but I managed to convince her."
"How did you convince her?"
Sona was a bit curious.
"With this."
Tatsuma took out a mask and put it on his face under Sona's puzzled gaze.
He said, "I can use magic to alter my appearance and physique, and then wear a mask to conceal my identity."
"As long as I don't use the Boosted Gear in battle, no one will know my identity."
"I see, doing this can indeed solve the problem to a certain extent." A hint of excitement flashed in Sona's eyes.
However, after hesitating for a moment, she still shook her head at Tatsuma. "I appreciate your kind intentions, but I won't need your help this time."
Tatsuma asked, "Why?"
"I'm well aware that my servants aren't strong enough, so I already thought of a way to solve this matter without resorting to force as early as yesterday."
Sona tapped the desk, summoning a chessboard to appear on the office desk in front of her.
She said, "I will return to the Underworld later and challenge my fiancé to a game of chess on the grounds of not marrying an idiot."
"Ten games of chess. If I lose one game, I lose. As long as I set this condition, the other party will definitely take the bait and accept my challenge."
"So you have to win all ten games."
"Yes, but I'm confident." Sona's face was full of confidence.
Seeing this, Tatsuma remembered her trait.
[Overclocked Thinking (Red): Forcibly enters a calm state when processing problems, and thinking speed greatly accelerates, entering bullet time.]
With the fully activated Overclocked Thinking, Sona had an absolute advantage in chess.
"Alright, then I wish you success."
Tatsuma felt a bit regretful. He thought he could repeat his success and play another Rating Game to farm more traits. Unexpectedly, Sona had already prepared a solution, so his intervention wasn't needed.
However, just as Tatsuma was about to leave, Sona suddenly called out to him.
"Cough! Tatsuma, can you do me a favor?"
"A favor?"
"Yes, I hope you can practice with me."
Sona sat down in front of the chessboard and said, "With your help, I should be able to increase my win rate to 100%."
Tatsuma raised an eyebrow. "100%? You're overestimating me, aren't you?"
A few days ago, when he was taking lessons from Sona, he had learned some knowledge about chess.
With the help of Limitless Potential and other traits, Tatsuma's learning speed was very fast. But compared to Sona, who was proficient in chess, he still had a considerable gap.
To this day, Tatsuma had only won against Sona once, and that was because she was careless and gave him an opportunity.
Tatsuma said, "When it comes to playing chess, I think it's more suitable for you to ask Rias for help than me."
"No, you are the most suitable."
Seeing that Tatsuma wanted to leave, Sona thought for a moment before replying, "How about this? As long as you can win one game against me, I'll fight you."
"Deal."
Tatsuma's eyes lit up, and he sat down opposite Sona.
A few days ago, when taking lessons at the Student Council, Tatsuma had used the excuse of sparring to fight all of Sona's peerage. Only Sona herself kept making excuses about not having time, constantly postponing a fight.
Since he had a rare opportunity, he naturally didn't want to miss it.
...
An hour later.
"Checkmate."
Tatsuma put down his piece, ending the game.
"...You won."
After a moment's pause, Sona replied with a complex expression.
She lost again.
And unlike the previous time when she was careless, she was defeated head-on this time.
From having the upper hand in the first game, to being evenly matched in the second game, and finally being completely suppressed in the third game.
Recalling Tatsuma's visible progress speed in the three games just now, Sona once again felt the gap between herself and him.
After sorting out her complex emotions, Sona asked, "According to our previous agreement, I will fight you next. When are you free?"
"I'm free right now."
Tatsuma replied, then changed the subject, "Sona, let's not rush the fight. After playing a few games with you just now, I suddenly realized you don't seem that strong."
"Are you sure it's okay to break off the engagement by playing chess? How about using my method instead?"
This way I can also farm more traits.
Sona replied, "Don't worry, I'm confident. As long as you practice with me for a few more days, the success rate of this plan will be 100%."
Tatsuma asked, "Are you really not considering my plan?"
"Sorry. On this matter alone, I don't want to trouble you for help."
"...Alright then."
Tatsuma sighed and set the daily chess time for lunch break as before.
After that, he took Sona out of school and went to Kuoh Town's outskirts for a simple spar.
[Congratulations on successfully defeating Sona Sitri, obtaining the purple trait 'Pure-Blooded Devil']
[Pure-Blooded Devil (Purple): The Devil's blood contains immense potential, Demonic power recovery speed +100%, Training effect +300%.]
"Not bad."
Looking at the trait that just dropped from Sona, Tatsuma's face showed satisfaction.
For him, training effect was the most important attribute.
Even though it was just a purple trait, combined with Limitless Potential, this trait's help to him was even higher than some red traits.
Temporarily putting the new trait into storage, Tatsuma and Sona prepared to return to school.
But just then, a red light suddenly rose from Tatsuma.
"Hmm?"
Tatsuma was stunned for a moment and took out a flyer inscribed with a magic circle from his pocket.
"What's wrong? Did something happen?" Sona asked when she saw this.
"Yuji seems to be in trouble."
Tatsuma activated the flyer, summoning a magic circle under his feet.
"I'll go check the situation. Can you help me take a leave from school?"