You can try searching on fanfiction platforms like Archive of Our Own (AO3). There are often a great number of fanfics about different pairings from 'Blue Exorcist', including Rin x Shura. Another option is FanFiction.net, though the quality may vary more there. You can also check out some Blue Exorcist - related forums or communities where fans might share their favorite fanfics or even write some themselves.
I would recommend AO3. It has a large and diverse collection of fanfics. Just type 'Blue Exorcist Rin x Shura' in the search bar, and it will show you a list of relevant stories. Some might be more to your taste in terms of writing style, plot, etc. than others. You can also follow some of the more popular authors in the Blue Exorcist fandom on these platforms, as they may write more Rin x Shura stories in the future.
Well, there are a few places. AO3 is a top choice because of its extensive tagging system. This makes it easy to find exactly what you're looking for, like a Rin x Shura fanfic. Additionally, Tumblr can be a good source. There are often fanfic recs (recommendations) on Tumblr blogs dedicated to 'Blue Exorcist'. Sometimes, fans will post links to their own fanfics or those they've discovered and really liked. However, make sure to respect the authors' rights and the rules of the platforms when accessing these fanfics.
Chapter 111, "A Narrow Escape from Desperation [3-in-1 Mega Chapter]", is the clearest early answer because the buildup finally cashes out in a real clash. The chapter turns that into something concrete by moving from If there were any chance to confront the rodent swarm directly,... to Looking at the enthusiastic volunteers, Xia Hong's expression was....
Chapter 108, "Long-tailed Rodent [3-in-1 Mega Chapter]", is the clearest early answer because it turns Xia Chuan's situation into a concrete plot event. The chapter turns that into something concrete by moving from The power of the swarming Cold Beasts was already something Xia Hong... to Without understanding why they're congregated here, trying to lead....
Chapter 49, "Da Shi Camp Annihilation [Please Follow!]", is the clearest early answer because it turns Xia Chuan's situation into a concrete plot event. A useful checkpoint is the way the scene starts with my leg, my leg..." "Boo hoo... and follows through with Perched on his son's back, Shi Qing first showed a flash of pain in....
Chapter 524, "Battle With The Captain", is the clearest early answer because the buildup finally cashes out in a real clash. The chapter gives readers a real answer by opening on Pressed on everyone and everything without exception. and ending on They stared at each other through the wreckage of what used to be a.... In story terms, the danger stops being abstract and the conflict around power growth becomes immediate, forcing the surrounding cast to react under pressure.
Chapter 159, "Blood and Flesh Wall, Has the Leader Not Broken Through Yet?", is the clearest early answer because it turns Mu Dong's situation into a concrete plot event. Early on, A few low-level Cold Beasts don't pose much of a problem, with so.... By the end, Some, sensing their own limits, imitated Mu Dong by tying the Iron....
Chapter 187, "Lu Sheng, Stealth Harvesting, Humiliation", is the clearest early answer because it turns Lu Sheng's situation into a concrete plot event. Early on, Disdain, of course, has its reasons.. By the end, And actually annexed the Mirror Immortal Camp!. Inside the broader trade and resources storyline, the chapter closes with "They definitely were. Those two bags must weigh tens of thousands of pounds.
Chapter 168, "Snow Bamboo, Longyou, Sudden Wealth", is the clearest early answer because it turns Meng Yi's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Chief, the corpses from earlier have all vanished. and follows through with So, over the years, we've only managed to collect a little bit.. By the close, How to manage and integrate these over three thousand people will..., and the chapter closes with "Chief, this is called Snow Bamboo.
Chapter 154, "Inheritance Rights, Strategic Contraction [Sorry for the Delay]", is the clearest early answer because Wood Puppet Monster gets a payoff that changes the stakes. A useful checkpoint is the way the scene starts with They still have the leisure to battle us, these fools!" "Hahaha,... and follows through with Xia Chuan, Luo Yuan, and Yue Feng clearly also realized, with traces....
Chapter 62, "Soul Capturing, Promoted to Intermediate", is the clearest early answer because it turns Wood Puppet Monster's situation into a concrete plot event. The setup is At this moment, the valley ground was littered with the fragmented..., but the pressure keeps building through Dense white lines burst forth from the Wood Puppet Monster's body,....
Chapter 117, "Teng Jiao Saliva and Poison Source [Two-in-One]", is the clearest early answer because it turns Yuan Cheng's situation into a concrete plot event. The setup is Although Teng Jiao is dead, the poison mist still hasn't dispersed..., but the pressure keeps building through No need to wait, pack up and let's go quickly!" Yuan Cheng's back was....