Perhaps Naruto has developed some special jutsu specifically for this situation in the fanfiction. He might have a jutsu that can temporarily paralyze Might Guy. When he sees Tenten in danger, he quickly activates this jutsu on Might Guy, then he goes to Tenten, checks if she is okay, and takes her to a secure location away from the threat of Might Guy.
Maybe Naruto uses his shadow clone jutsu to distract Might Guy while he rushes in to grab Tenten and get her to safety.
In the fanfiction, it could be that Naruto taps into his newfound Sage Mode powers. He quickly assesses the situation where Tenten is in danger from Might Guy. Using his enhanced speed and strength in Sage Mode, he intercepts Might Guy's attack meant for Tenten and then uses his Rasengan to create a diversion, allowing him to carry Tenten away to a safe place.
It could be that Might Guy is under some sort of mind - control. So, without his normal self - control, he attacks Tenten, making it necessary for Naruto to save her.
Well, in fanfictions there could be various ways. He might use his Rasengan to create an opening in Gi Sensei's defenses and then rush in to save Tenten. Another possibility is that Naruto uses his speed and agility, enhanced by the Nine - Tails' chakra perhaps, to dodge Gi Sensei's attacks and reach Tenten before she gets hurt.
Naruto could use his Uzumaki bloodline's chakra reserves. He might overwhelm Might Guy with a large number of shadow clones, confusing him and creating an opening to save Tenten.
Well, perhaps in this fanfiction, Might Guy is possessed by some sort of dark force. This makes him turn on Tenten during a sparring session. Naruto, being the hero he is, arrives just in time. He first tries to talk to Guy, but when that fails, he uses his speed and agility, skills he's honed over years of fighting. He quickly grabs Tenten and gets her to safety, then he has to figure out how to free Guy from the dark influence.
I'm not sure who Gi is in this fanfiction as I haven't read it. But it could be an original character created by the author of the fanfiction, perhaps a villain who poses a threat to Tenten.
Well, Naruto has his Nine - Tails chakra. He could potentially tap into that power to either overpower Might Guy or create some kind of shield around Tenten. He might also use his Rasengan, but in a non - lethal way to stop Might Guy's attacks long enough to protect Tenten. Also, Naruto is known for his quick thinking and adaptability in battle, so he could come up with a unique strategy on the spot depending on the situation.
In some fanfictions, Naruto might reshape Tenten by influencing her training methods. For example, he could introduce his own unique ways of chakra control and combat strategies, which might inspire Tenten to become more creative in her use of weapons and ninjutsu. This could lead to her developing new techniques and becoming a more well - rounded ninja.
Naruto could use his shadow clone jutsu to create distractions. While Gai is busy dealing with the clones, Naruto can quickly get Tenten to a safe place.
One possible antagonist could be a rogue ninja from another village. They might target Tenten for her unique weapon - handling skills, thinking they can use her to create powerful weapons for themselves. Naruto would then have to face this ninja to save Tenten.
Well, in this fanfiction, Naruto might save Tenten from a powerful enemy. Maybe she's captured during a mission and Naruto uses his shadow clones and Rasengan to rescue her.