One common theme could be the exploration of their relationship's growth. It might start from Sesshomaru's initial coldness towards Rin and how it gradually thaws as they get closer. Another theme could be the acceptance within the demon world, as Sesshomaru is a powerful demon and Rin is human - or at least was human originally. And there could also be themes of family, as they build a life together and perhaps face issues related to having children or integrating into each other's 'familial' circles.
Well, a frequent theme is the transformation of their bond. In many of these fanfictions, we see how Rin's unwavering loyalty to Sesshomaru blossoms into love, and how Sesshomaru comes to terms with his own feelings. Also, cultural differences between the human and demon worlds often play a role. How do they bridge the gap? How do they handle the different values and traditions? These are all things that are commonly explored in such fanfictions. And of course, there's the theme of power dynamics. Sesshomaru is so much more powerful than Rin, so how does that affect their relationship, especially when they are married?
Common themes include the development of love against all odds. Given that their relationship in the original series was more of a protector - protected one, fanfictions often focus on how that changes into a romantic relationship. There may be themes related to the passage of time, as Rin has to grow up for a romantic relationship to be possible. Additionally, themes about loyalty and trust are prevalent. Since Sesshomaru has a complex personality, Rin's loyalty has to be tested and proven time and time again in these stories. And finally, the idea of building a new world or a new life together, away from the chaos of the original Inuyasha plot, is also a common theme.
Chapter 193, "Don't Die Yet", is the clearest early answer because it turns Damon's situation into a concrete plot event. It opens with The group paused their trip through hell as they waited for Daveon to... and closes on I took down about twenty of them before I encountered my first real.... The key payoff is that the chapter closes with As the demons drew closer, their grotesque forms becoming clearer, Damon, Anaya, and Daveon fell into formation.
Chapter 419, "I Didn't Lose", is the clearest early answer because it turns Lyone's situation into a concrete plot event. The chapter gives readers a real answer by opening on The faintest scrape of hinges reached Damien's ears. and ending on Lyone's chest heaved, his training evident in every strike.. In story terms, the chapter closes with "Hehe...
Chapter 419, "I Didn't Lose", is the clearest early answer because it turns Lyone's situation into a concrete plot event. A useful checkpoint is the way the scene starts with The faintest scrape of hinges reached Damien's ears. and follows through with I guess that was enough to finally earn a praise, huh?" Lyone forced.... By the close, Lyone's chest heaved, his training evident in every strike., and the chapter closes with "Hehe...
Chapter 267, "Arriving In Ryedale", is the clearest early answer because it turns Damien's situation into a concrete plot event. The setup is Damien took a deep breath, stretching his sore muscles as he surveyed..., but the pressure keeps building through The sky was now painted in hues of orange, red, and gold, the rising....
Chapter 314, "A Talent Holder", is the clearest early answer because it turns Damien's situation into a concrete plot event. The chapter turns that into something concrete by moving from There were no sunbeams slicing through the curtains, no cheerful... to I saw the shimmer in the air, the wings, your hair." "It's not a....
Chapter 173, "The Battle In The Cavern", 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 The small infirmary Arielle had prepared in Westmont was bustling... to Having ensured the captives reached Westmont safely, there was no....
Chapter 221, "The Cooling Reverse Technique", is the clearest early answer because Daveon gets a payoff that changes the stakes. The chapter gives readers a real answer by opening on The blazing heat of the First Layer of Hell was no longer as... and ending on That's the inferno growing inside you," he said softly.. In story terms, the chapter closes with "Yes, Miss Leana!" All three students or rather wards of hers replied with riled up tones.
Chapter 66, "Caught In Between", is the clearest early answer because it turns Damien's situation into a concrete plot event. A useful checkpoint is the way the scene starts with «Griffin: A majestic hybrid blend of both a lion and an eagle that... and follows through with Your gifts and Golden Tickets are welcome as well!.
Chapter 370, "Elias's Encounter", is the clearest early answer because it turns Elias's situation into a concrete plot event. It opens with Only a presence that glowed behind the eyes, soft and colorless—like... and closes on The third, a metal cube vibrating at an almost invisible frequency,....
Chapter 359, "Dealing With Merging Demons", is the clearest early answer because it turns Damien's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Damien's feet slammed into the earth like a warhammer crashing from... and follows through with But she felt the corner of his mouth curve upward..