One of the most iconic villains in videogame history is Sephiroth from Final Fantasy 7, and this character's presence in Final Fantasy 7 Remake has stirred up a lot of confusion and controversy. The developers have disclosed some information that somewhat clears up his role in the 2020 game: they have confirmed there are actually four different forms of Sephiroth in FF7 Remake.
The Masamune-wielding antagonist is a complex character with a complicated backstory in Final Fantasy 7, and the idea of four Sephiroths can sound frustrating for those who wanted a remake that didn't deviate from the original. It should be comforting to know that this does mean there are actually four separate physical Sephiroth bodies walking around in Final Fantasy 7 Remake. Sometimes when he is shown, it's in the form of a memory.
This information is not new. It was released in the Final Fantasy VII Remake Ultimania which became available less than two months after the game's release. Ultimania books are artbooks and guides that contain supplemental materials for the games. Unfortunately, the FF7 Remake Ultimania book only has a Japanese edition. Luckily, a dedicated fan and Tumblr user - aitaikimochi - has translated most of it. The following will help explain why sometimes only Cloud can see Sephiroth.
[Warning: Spoilers for Final Fantasy 7 Remake regarding when each version of Sephiroth appears below. This includes late chapters of the game and will be presented chronologically]
Final Fantasy 7 Remake: Sephiroth's Four Forms, Explained
The four types of Sephiroth that appear in the game are: an "Illusion" only Cloud can see; a black-hooded man ("Black Hood") that looks like Sephiroth; a "Flashback" version; and an "Unknown" existence that Cloud and the others perceive as Sephiroth. The translation of Final Fantasy VII Remake Ultimania elaborates on exactly when each of these forms appear.
The first time Sephiroth is shown in FF7 Remake is the Illusion in the Sector 8 neighborhood during the fire scene. This is the same one Cloud sees when he meets Aerith in FF7 Remake. When Cloud is at Stargazer Heights in the Sector 7 slums, he sees the first Black Hood that turns out to be Marco with the number "49" tattooed on his arm. The Illusion shows up again when Cloud is sleeping, as an auditory hallucination, and in the church in the Sector 5 slums when he tells Cloud, "I am your everything." Another Black Hood is next seen in the Sector 5 slums at the kids' hideout. This time it turns out to be a man with the number "2" tattooed on him, and the tattooed hooded figures were explained in the original Final Fantasy 7.
The next Sephiroth form in Final Fantasy 7 is seen after the Sector 7 plate drops when the gang is headed back to Aerith's house. This is the first time the Flashback is shown, in which Cloud recalls him saying, "within my veins flows the blood of the Ancients," with a white background. Immediately after, the Illusion Sephiroth seems to appear before Cloud and says, "You have failed again, I see. But through suffering, you will become strong." No wonder his presence is confusing when different versions are juxtaposed like this.
The Illusion appears later, right after the immersive video presentation inside the FF7 Remake's Shinra building. Only Cloud can see it. In the following scene, a surprised Palmer sees a Black Hood (Marco #49) walk by. Later, when the party sees Jenova, Cloud recalls the Flashback talking to her. The Ultimania states that because of the Jenova cells, the rest of the party can now see Sephiroth, as shown afterward when Tifa grabs Cloud. However, it's the Black Hood version, which is later shown carrying Jenova on the surveillance camera. This form is also the one in President Shinra's office and following that scene, the other Black Robe (#2 tattoo) jumps from the rooftop with Jenova.
At the end of the highway, Cloud almost crashes when an Illusion appears. Right after and from here on out, every Sephiroth shown is the Unknown type. The Ultimania notes that this Sephiroth refers to himself with a different pronoun in the Japanese game - one that he only used before FF7's Nibelheim incident. According to aitaikimochi's translation, the title for this section in the Ultimania is called, "Who exactly is the Sephiroth that appears at the end of the game?" Considering this and all the other mind-blowing events that happened in the finale of Final Fantasy 7 Remake, the Unknown's motives seem very unclear. Still, hopefully these tidbits from the Ultimania help make sense of Sephiroth's confusing and sometimes contradictory presence throughout the game.
Source: Final Fantasy VII Remake Ultimania (translation by aitaikimochi)