naruto lost his smile

How about 'The Shattered Dream'? This title implies that someone had a big dream or aspiration which was completely destroyed. For example, a young athlete who has trained all their life for the Olympics but then gets injured in a way that they can never compete again. It sets a very tragic tone right from the start.

His relationship with Sasuke could become very different. Without the memories of their rivalry and friendship, Sasuke might see Naruto as a completely different person, and Naruto might not understand Sasuke's complex feelings towards him at all.

Well, in such a fanfiction, Naruto might find himself in a strange new land where he has no idea how to get back home. Maybe he loses his memories and has to start from scratch to figure out who he is and what his purpose is.

Naruto might become more cautious. Losing an arm would make him realize his vulnerability more. He would probably be more strategic in battles, relying less on brute force and more on his intelligence and remaining ninja skills.

Sasuke could be one of them. Despite their past differences, Sasuke might sense that Naruto is in trouble and come to his aid. After all, they have a deep connection.

He took it with a smile. The smile was all over his face.

An alien race that is highly intelligent but physically weak. They see Naruto as a powerful protector. In return for Naruto's protection, they offer him their advanced technology which could be crucial in his journey back to his world. For example, they might give him a device that can create wormholes to different parts of the universe.

One interesting plot could be Naruto being found by a hidden group who wants to use his power for their own ends while he's in his memory - lost state. They could manipulate him into believing he's one of them.

Perhaps an old enemy from Naruto's past that was thought to be defeated has resurfaced. This enemy might have targeted Naruto's wife as a way to get revenge on Naruto for their previous defeats. They could be using her as a bait to lure Naruto into a trap.

One possible storyline could be that Naruto's wife was killed during a major battle against a new and powerful enemy. This would send Naruto into a deep state of grief and depression, perhaps causing him to question his purpose as a shinobi. He might then embark on a journey to find the true cause of her death and seek revenge.