Happy, the blue flying cat, could be included. His ability to fly could help in scouting areas and his positive attitude could lighten the mood during difficult times. Another good character would be Wendy. Her healing magic could be crucial if Ren or Sherry get injured during their adventures. Also, her connection to the sky dragons could provide some unique plot elements, like learning about a long - lost sky dragon - related magic that could help them in their quest.
Natsu could be a great addition. His brash and powerful nature could contrast with Ren and Sherry's more calculated and magical - knowledge - based approaches. He could join them on a mission and provide the muscle when they encounter tough opponents. Also, Lucy would be good as she has a wide range of celestial spirits that could be useful in different situations. Her kind and curious personality would also add an interesting dynamic to the group.
Sherry could be developed by exploring her insecurities about her magic. Maybe she has always felt that her magic was not as powerful as others in Fairy Tail. Ren could help her gain confidence by believing in her. For Ren, his character could be developed through his backstory. He might have a past that makes him hesitant to get close to others, but Sherry's kindness breaks through his barriers.
One possible plot could be that Sherry and Ren team up for a difficult mission in the Fairy Tail world. They might face a powerful dark wizard who has the ability to manipulate time. Sherry's magic could be crucial in deciphering the wizard's spells, while Ren uses his combat skills to protect Sherry during the battles. Along the way, they start to understand each other's pasts and form a deep bond.
Maybe a plot where Ren gets cursed and Sherry has to find a way to break it. She could search through different magic libraries and consult with other mages in Fairy Tail. During this time, Ren is struggling with the effects of the curse, which could be something like slowly losing his magic power. Their friendship deepens as Sherry is determined to save him, and in the end, she discovers a rare spell that breaks the curse.
Goku could be a great addition. Maybe he could offer some advice to Vegeta about his tail based on his own Saiyan experiences. Another good character would be Trunks. He could be involved in a story where he discovers something new about his father's tail.
Natsu could be a great character to pair them with. Since he's also a dragon slayer, there could be some interesting interactions and competitions among them. They could learn from each other's dragon slayer techniques.
Natsu could be a great character to pair them with. Natsu's fiery and impulsive nature would contrast well with Lucy's more level - headed and Erza's strict personality. They could all go on an adventure together, with Natsu leading the charge into dangerous situations, Lucy using her celestial spirits for support, and Erza keeping them in line. Gray is also a good option. His cool - headedness and ice - make magic could add an interesting dynamic to the group, especially when paired with Natsu's fire magic and the celestial and re - equip magic of Lucy and Erza.
In a crossover with 'One Piece', they could be paired with Luffy. Luffy's carefree and determined nature would contrast well with Freed and Laxus. They could all be on a quest to find a magical treasure that has power over both their worlds. Luffy's Gum - Gum powers would be interesting to see alongside Freed's rune magic and Laxus' lightning.
Definitely include Natsu. His enthusiasm and positive energy can add some light - hearted moments to the story. He could also be the one to accidentally push Cana and Gildarts closer together, like by getting them into a situation where they have to rely on each other. Lucy would also be a good addition. She's a good friend to Cana and can offer a different perspective on love and relationships, having her own experiences in the guild.
Obviously Naruto himself. He is the main character and his connection to the One Tail is the core of the story. Kakashi would also be a great addition. His wisdom and experience can help Naruto deal with the challenges related to the One Tail, like teaching him new ways to control it.
Obviously, Natsu Dragneel is a must - include. His adventures in Fairy Tail are well - known, and his growth as a wizard and a person are great elements to explore in a fanfiction. Then there's Wendy Marvell, who has a connection to the Dragneel family through her dragon - slayer magic. She can bring a different perspective and her own set of skills. And of course, Gajeel Redfox, another dragon - slayer, can be included as he has his own interactions and rivalries with the Dragneel family members, especially Natsu. His rough - around - the - edges personality contrasts well with the Dragneel family's overall vibe.