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English
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Published:
2026-02-01
Updated:
2026-02-19
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6,842
Chapters:
4/?
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33
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The Friend of Teruhashi (Saiki k x reader slowburn)

Summary:

Y/N is the best friend of Teruhashi. Their friendship had started off strong, but as the months went on, the effect of Teruhashi's beauty had backfired on them. Her beauty had made them began to lose their own charm believing that they would never be able to add up to her. Teruhashi doesn't notice her friends declining mental health, but Kusuo does.

Notes:

Tw: heavy topics. For now the mentions are light, but I plan on getting deeper in...heh ...🤑

(See the end of the work for more notes.)

Chapter 1: Thick sweaters and deep feelings

Chapter Text

Teruhashi, nuisance number four, as he called her, constantly tried to surround Kusuo with herself. She had good intention, but...well, she really only liked him because he ignored her. He supposed he could see why, where she was coming from. 

Nobody really treated her like a person, they just saw her on the outside. They saw her facade, they saw the perfect pretty girl she portrayed herself as.

She was pretty annoying at times, though. That doesn't mean he didn't care about her—but she definitely wielded some flaws deep down, while other's only saw how she was on the surface. Perfect, beautiful, and just another hot chick.

Unfortunately her main flaw was narcissism—a lot of the times it seemed like she really only cared about herself, and how things benefited her, not the others around her. This included her best friend, Y/N. 

Y/N never really hung out with everyone. They preferred to keep to themselves, but they weren't always that way. Once upon a time, they were your typical, bubbly teenager. Eager to make new friends and show said friends all the love in the world to show their appreciation.,

Well they did make a new friend, Teruhashi. Within the first few months of being her friend, Y/N had slowly backed into a shell, their confidence zeroing down to practically nothing, the spark in their eyes missing. 

Kusuo had only noticed because of how Teruhashi practically neglected her friend's feelings for her own. He'd noticed Y/N's thoughts of trying to validate their friend no matter what she did, he noticed how everytime Teruhashi was evidently passive aggressive with them, they would get quieter every time.  

Eventually it got to the point they barely said a word anymore, their grades declining—his eyes couldn't help but trail over to the 'D-' circled in red pen at the top of their test in Calculus. The old Y/N would have cared, would have instantly fixed it, but now, they simply ignored it, though their own mind berated them with how much of a disappointment and a failure they were. 

While he didn't talk to Y/N often, he didn't mind them. They were actually quite nice, they were just...reserved, and timid. At least that's what people thought. The truth was that they didn't have the confidence to speak anymore—anytime they tried to around Teruhashi, they were always interrupted, always ignored, so they learned to stop talking. 

Teruhashi was stunning, evidently, she was beautiful, blessed by the Gods—literally—and Y/N had slowly began to accept that they would never be good enough, that they would never even be within a vision of being in the same league as their best friend. They'd accepted that she didn't really care, or...maybe she did, but who were they to know? She brushed them off too often for them to truly know. 

When the class had taken their school trip to Okinawa, Y/N didn't change into a swimsuit or anything, they kept their sweater on, and left on a pair of jeans as well. Kusuo took note of this when Y/N sat down a few beach chairs down from him. He stared at them for a moment, not so subtly, as they leaned back, staring out into the ocean.

He watched as they shifted themselves into comfortablity on the chair, their chest rising and falling as they took a deep breath. He couldn't help but wonder why Teruhashi wasn't with them, their thoughts didn't suggest anything, they were simply thinking of how nice the ocean looked. He peeled his eyes away from them, leaning back and letting them flutter closed. He' hoped to relax a bit after a long trip. He'd stopped quite a few disasters from happening on the way here, so...everything should be good. At least for now.

Y/N trailed their fingers slowly over their arms, before bringing their knees to their chest, eyes fluttering shut as they took a deep breath, the summer breeze felt nice on their skin, but the sweater they wore also felt a bit suffocating. With Teruhashi here, they felt they couldn't wear what they wanted to.  

They didn't feel like she had bad intentions, it wasn't her fault she was pretty! And her win wasn't their loss, but they felt like they couldn't compare. It's not like they lacked beauty, and of course nobody would really be looking at them, but they felt that their own eyes were the ones that held the most judgement. Maybe it was all in their head. Maybe they were just being overly envious. 

They opened their eyes and tilted their head back against the beach chair, looking up into the sky. They could feel their body getting hotter by the second in this sweater. They sighed deeply as they brushed their hair back. 

'Dang it... should'a worn a different shirt. Maybe I should've just sucked it up and slipped on a swimsuit...it's hot as buns out here.' They let their shoulders drop as they exhaled, glancing in a different direction. 

They closed their eyes once more, letting the noises around consume them. The sea lapping at the shore line, the sound of seaguls yelping, calling out to each other in their own language. They could hear the sound of laughter both in the water and on land, groups of friends gathered in their own clusters, while outliers kept to themselves, within their own domains. The sounds were constant. The lack of change was refreshing to them. Eventually, though, a voice, significantly closer and clearer than the other's, broke through. 

"You should go swim." Said voice sounded. They recognized the voice, and looked over to see Kusuo looking at them. 

They stayed silent a moment, contemplating his words. They slowly turned their gaze back to the water, considering the option. They just hated seeing themselves swimsuit clad. "...I don't really feel like it right now," Y/N murmured. 

"But you're in the mood to lay in a beach chair in clothing that will give you a heat stroke?" 

Kusuo watched Y/N go quiet and then just shrug. 

"You're not gonna have much fun doing that." He said after a moment. "I'm sure your friends are waiting for you." 

Y/N looked to Teruhashi, who was being oggled while she played beach volleyball with Chiyo. Their gaze lingered for a hot second before they simply shook their head and looked away. 

Kusuo's eyes narrowed faintly. For some reason he wanted to help them. He wanted them to enjoy the trip. 

"Is something wrong?" 

"Oh, uhm...no, nothing's wrong. Why" Y/N questioned.

"You're acting off. It's weird." 

Y/N swallowed quietly, looking at him in silence, trying to form some sort of coherent response. "...no I'm not," they said

"You are," he said bluntly. He watched as they slowly looked away, rubbing their arms quietly. "But if you don't wanna tell me about it...I guess I'll understand." He said. He already knew what was wrong. He wasn't the best at comfort, but...he was trying, without being too outright. 

"Thanks for the concern, but I'm fine. Just don't feel like swimming, is all." They said. 

Kusuo watched before he gave a short and curt nod, looking away and closing his eyes again. He himself let the area around consume him, before it slowly faded when he fell into slumber in the warm sun. Basking like a cat.