One possible reason could be that Naruto is so focused on his goal of becoming Hokage. His mind is occupied with training and achieving power, so he seems cold to Sakura. He might not have the time or mental space to show her more warmth.
One reason could be that Naruto has grown weary of Sakura's unrequited love for Sasuke. He might feel like she's always focused on Sasuke and doesn't truly see him, Naruto. Another aspect could be that Sakura's constant nagging or her over - emotional outbursts have started to grate on Naruto over time. Maybe he's also tired of having to be the one to always cheer her up when Sasuke - related things go wrong.
It could be due to a new jutsu he's trying to master that has some side effects on his emotions. Maybe it's a powerful ice - based jutsu that's making him cold in nature as well.
One reason could be that Naruto is focused on his own goals like becoming Hokage and he might see Sakura's feelings or her actions as distractions. He has a lot on his plate and may not have the time or energy to deal with her in a warm way.
One possible reason could be that Naruto realizes Sakura's unrequited love for Sasuke. He might feel tired of always being in a one - sided emotional situation with her. Another reason could be that Naruto has his own goals and growth to focus on. His journey to become Hokage and protect the village requires all his attention, leaving little room for his previous feelings for Sakura.
It could also be a part of some sort of training gone wrong. In the world of Naruto, they often engage in intense training. If Sakura and Naruto were sparring and Sakura pushed Naruto too far, perhaps by taunting him about his strength or his progress compared to Sasuke, Naruto might lose his temper and punch her.
One reason could be for shock value. Writers might want to create a story that stands out from the typical Naruto fanfictions. By introducing such a dark and unexpected element like abuse, they can grab readers' attention. Another reason could be to explore a different side of Sakura's character. Maybe in this fanfiction, they want to show a corrupted or extremely stressed version of Sakura who takes out her frustrations on Naruto.
Maybe Sakura makes a decision that endangers herself or the team without consulting Naruto. In the world of Naruto, they are a team, and Naruto values his comrades. If Sakura does something reckless like that, it could make him angry.
One reason could be that Naruto has been through a lot and is emotionally drained. He might see Tsunade as a source of comfort and stability, so he calls her mom. His coldness could be a defense mechanism to hide his vulnerability. Another reason could be that he has seen how Tsunade cares for others in the village, and he subconsciously wants that kind of motherly love for himself.
One possible reason could be that Naruto has his own unrequited love for someone else and he is trying to distance himself from Sakura to avoid leading her on. For example, if he has deep feelings for Hinata, he might be cold towards Sakura to make his own feelings clear.
One possible reason could be Naruto's over - eagerness to prove himself. Naruto is always trying to show that he's strong and capable, and sometimes this might come across as him not considering Sakura's feelings or opinions. For example, he might rush into a dangerous situation without consulting her, which could lead to an argument as Sakura is also a capable ninja who wants to be part of the decision - making process.