Another scenario might be a situation where Natsu accidentally eats some magic - enhancing food that makes his emotions go wild. Lucy has to figure out how to calm him down and in the process, they realize deeper feelings for each other. For example, Natsu might start uncontrollably shooting fire everywhere, and Lucy uses her whip to lead him to a safe place where she can try to reverse the effect.
One interesting scenario could be when the baby's first magic manifestation occurs. It might happen during a guild party and startle everyone. Another scenario is that the baby gets lost in the guild's large building, and all the members, including Natsu and Lucy, go on a frantic search. A third scenario could be the baby developing a strange bond with an unexpected celestial spirit.
One popular scenario could be after a major battle where they both realize their deep feelings for each other. Natsu, being the impulsive and passionate character he is, might just grab Lucy and plant a kiss on her. Another could be in a moment of great celebration in the guild. With everyone around them having a great time, Natsu and Lucy get caught up in the moment and share a kiss. And sometimes, it might be in a more private, tender moment. Maybe Lucy is feeling down, and Natsu tries to comfort her in a more intimate way, leading to a kiss.
There are also scenarios where Lucy is targeted because of her celestial spirit magic. Natsu, being aware of the power and danger associated with it, ensures that no one can use Lucy's magic against her or the guild. He'll stand between her and any magic - user who tries to manipulate or harm her because of her unique abilities.
In a battle against a group of powerful enemies, Natsu overexerts himself and is on the verge of being defeated. Lucy steps in. She first summons all of her available Celestial Spirits to create a powerful defensive formation around Natsu. Then, she combines her own magical attacks with those of her spirits to drive the enemies away. After that, she uses her healing magic (if she has developed such in the fanfiction) to nurse Natsu back to health.
A great Natsu and Lucy fanfiction might involve a time - travel plot. For example, they could go back in time to the founding of Fairy Tail. This would give them a chance to meet the original members and change the course of history. Along the way, their relationship would surely evolve as they face the challenges of the past. It's a really cool concept that many fanfiction writers like to explore.
A plot idea could be that an old enemy from Natsu's past returns and targets Lucy to get to Natsu. Natsu then has to go all out to protect Lucy, and in the process, they both learn more about each other's fears and insecurities. Or perhaps there is a magical competition in which Lucy and Natsu team up, and they face various challenges that test not only their magical abilities but also their friendship and trust in each other.
One interesting scenario could be Natsu and Minet going on a quest together. They might face a powerful magical beast and have to combine their skills to defeat it. Natsu's fire - based attacks and Minet's unique abilities could create a great synergy.
In some fanfictions, Natsu and Erza might have a moment where they confide in each other about their pasts. Erza could open up about her time in the Tower of Heaven and Natsu about his search for Igneel. This sharing of deep secrets would bring them closer and change the dynamic of their relationship from just being guild mates to something more like true friends who support each other unconditionally.
One great Nalu fanfic is 'A New Adventure'. It takes place right after the main story and shows Natsu and Lucy going on a quest that was hinted at in the original series but never fully explored. Another is 'Nalu's Bond', which delves deep into their relationship, showing how they support each other through tough times. There's also 'Fairy Tail: Nalu's Destiny' that has an alternate universe concept where they have different roles in the guild but still end up being drawn to each other.
One interesting Lucy x Natsu fanfiction could be 'A Bond Beyond Magic'. In this fanfic, Lucy and Natsu go on a journey to a hidden magical realm where they have to rely on their bond more than ever. Their relationship deepens as they face challenges that test not only their magic but also their feelings for each other.