Gaara would probably be intrigued yet guarded. He has a deep understanding of pain and isolation, so he might sense that in the'monster' too. But his past traumas would make him approach the situation with caution. He might watch from a distance at first, trying to figure out if the'monster' is a threat or not. If the'monster' shows any signs of kindness or vulnerability, it could pique his interest further.
Well, in this story, the'monster' aspect might be more of an internal feeling. Gaara, being a complex character, would understand that. Maybe the story is about how the'monster' character tries to hide their true self from Gaara at first. But as they interact more, Gaara senses the pain and loneliness. Their love story could then develop as they both help each other heal from their past wounds.
You could try to understand why they see you that way. Maybe have an open conversation with them to clarify things.
Tsunade might react with concern. Since she is a caring and experienced figure in the Naruto world, she could be worried about the implications of Gaara's strong feelings for his sister. She might wonder if there are any underlying issues or if Gaara is in some sort of trouble related to his family. So, she could start to question Gaara gently about his family situation and how this love for his sister has developed.
The friends from Gaara's village, like Temari and Kankuro, would be very protective. Temari would likely give Naruto the 'big sister' talk, warning him to take good care of Gaara. As for Naruto's friends, they would support him wholeheartedly. Choji might bring over some of his favorite snacks for Gaara, thinking it would be good for the baby. And Hinata would be quietly supportive, maybe knitting some baby clothes in her spare time.
Often, Naruto's female characters are paired with Gaara. For example, Hinata. Since Hinata is a kind - hearted and shy character, her relationship with the initially cold - hearted Gaara could be an interesting exploration of how two different personalities come together.
Temari and Kankuro would probably be very protective. They've always been close to Gaara, and seeing him as a baby would bring out their nurturing sides. They'd do everything they could to keep him safe and find a way to turn him back. Naruto, on the other hand, would be shocked at first but then would see it as his duty to help. He has a strong sense of justice and friendship, and he wouldn't abandon Gaara in such a state.
Naruto, being the friendly and optimistic one, would likely be excited for Gaara. He might encourage Gaara to be more open about his feelings towards Sakura. He could offer advice based on his own experiences with Hinata. Sasuke, though, would probably be aloof. He has always been more focused on his own goals and revenge. He might view Gaara's crush as a distraction for Gaara and tell him to focus on more important things, like protecting his village. However, deep down, he might also hope that Gaara can find some happiness.
The ninja from other villages would also have different reactions. Those who knew Gaara and his past might be more understanding of Naruto's new behavior, thinking it's just a phase or a way for Naruto to grow. However, those who were enemies of Gaara in the past might see Naruto's change as an opportunity to attack, believing that he has become more vulnerable or unpredictable. The Akatsuki members, if they are still around in the fanfic, might try to take advantage of Naruto's new state, seeing it as a chance to capture him or use his power for their own evil purposes.
Sakura might be a bit surprised at first. She has always seen Naruto as a friend, but she would quickly come to support him. She knows how much Naruto values his relationships, and if he has found love with Gaara, she would be happy for him. Kakashi would be very accepting. He has always believed in Naruto's judgment and would see this as another step in Naruto's journey to change the ninja world. Shikamaru would probably be the one to think about all the political implications but in the end, he would also support it as he trusts Naruto.
His powers would also develop in new ways. He could learn to combine his sand powers with Fairy Tail magic. For example, he might learn how to use fire magic to heat up his sand and make it more powerful in attacks. Emotionally, seeing the love and loyalty in Fairy Tail could make him less cold and distant. He may start to value friendship more and his past traumas might start to heal as he is surrounded by such a positive and accepting group.