In the tenth and eleventh centuries, de Visser says that tengu were thought to be “a mountain demon” that caused trouble in the human world (38).
In stories from this period, tengu were portrayed as enemies of Buddhism (de Visser 43).
Later,  tengu were no longer seen as enemies of Buddhism specifically, but were portrayed as wanting to “throw the whole word into disorder” (de Visser 67).
According to de Visser, the reason Sōjōbō trains Yoshitsune in martial arts is to start a war (48).

In the Gikeiki, a text concerning the life of Yoshitsune, Sōjōgatani or Bishop's valley is described as being the location of a once popular temple that is now deserted except for tengu (qtd.
in de Visser 48).
According to the text, when evening approaches “there is a loud crying of spirits” and whoever visits the valley is seized by the tengu and tortured (qtd.
in de Visser 48).
A similar phenomenon is called kamikakushi.
Kamikakushi involves the kidnapping of human beings by a supernatural entity, such as a tengu (Foster 135).
It involves the disappearance of a child, usually a boy, followed by their return at a new and strange location and in a seemingly altered state (Foster 135).
Cases of kamikakushi can be caused by any yōkai, but tengu are often said to be involved (Foster 137).
Michael Foster says that the legend of the young Yoshitsune’s interaction with the tengu “fits the pattern” of a kamikakushi kidnapping (Foster 137).

In the fourteenth century, de Visser says, there is a change from all tengu being portrayed as bad to distinctions made “between good and bad tengu” (93).
Foster says that in variations of the legend of Sōjōbō and the young Yoshitsune, the tengu are portrayed as benevolent and helpful as they attempt to help the young Yoshitsune defeat the clan who killed his father (Foster 135).

Foster quotes dialogue from a work called Miraiki (Chronicle of the Future) to demonstrate the idea of the tengu being portrayed in a more benevolent way.
After the subordinate tengu see the young Yoshitsune practising near the temple on Mount Kurama, they explain that their prideful ways prevented them from becoming Buddhas and instead caused them to become tengu (Foster 134).
Then they say:
But even though this pride caused us to fall into this path, there is no reason we should not know pity.
So let us help Ushiwaka, teach him the method of the tengu so he can attack his father’s enemy (qtd.
in Foster 134).

 
The portrayal of the tengu, and Sōjōbō specifically, as sympathetic to the young Yoshitsune and his desire to avenge his father, is also shown in the Noh play Kurama-tengu (“Kurama-tengu (Long-nosed Goblin in Kurama)”).
In the play, the Great Tengu represents the figure of Sōjōbō.
The Great Tengu says he his impressed with the Ushiwakamaru character, the young Yoshitsune, for his respectfulness and admirable intentions.
Not only does he help Ushiwakamaru by training him to become a great warrior and defeat his enemies, he also promises to protect him and support him in future battles.
In the tenth and eleventh centuries, de Visser says that tengu were thought to be “a mountain demon” that caused trouble in the human world (38). In stories from this period, tengu were portrayed as enemies of Buddhism (de Visser 43). Later,  tengu were no longer seen as enemies of Buddhism specifically, but were portrayed as wanting to “throw the whole word into disorder” (de Visser 67). According to de Visser, the reason Sōjōbō trains Yoshitsune in martial arts is to start a war (48).
In the Gikeiki, a text concerning the life of Yoshitsune, Sōjōgatani or Bishop's valley is described as being the location of a once popular temple that is now deserted except for tengu (qtd. in de Visser 48). According to the text, when evening approaches “there is a loud crying of spirits” and whoever visits the valley is seized by the tengu and tortured (qtd. in de Visser 48). A similar phenomenon is called kamikakushi. Kamikakushi involves the kidnapping of human beings by a supernatural entity, such as a tengu (Foster 135). It involves the disappearance of a child, usually a boy, followed by their return at a new and strange location and in a seemingly altered state (Foster 135). Cases of kamikakushi can be caused by any yōkai, but tengu are often said to be involved (Foster 137). Michael Foster says that the legend of the young Yoshitsune’s interaction with the tengu “fits the pattern” of a kamikakushi kidnapping (Foster 137).
In the fourteenth century, de Visser says, there is a change from all tengu being portrayed as bad to distinctions made “between good and bad tengu” (93). Foster says that in variations of the legend of Sōjōbō and the young Yoshitsune, the tengu are portrayed as benevolent and helpful as they attempt to help the young Yoshitsune defeat the clan who killed his father (Foster 135). 
Foster quotes dialogue from a work called Miraiki (Chronicle of the Future) to demonstrate the idea of the tengu being portrayed in a more benevolent way. After the subordinate tengu see the young Yoshitsune practising near the temple on Mount Kurama, they explain that their prideful ways prevented them from becoming Buddhas and instead caused them to become tengu (Foster 134). Then they say:
But even though this pride caused us to fall into this path, there is no reason we should not know pity. So let us help Ushiwaka, teach him the method of the tengu so he can attack his father’s enemy (qtd. in Foster 134).
 
The portrayal of the tengu, and Sōjōbō specifically, as sympathetic to the young Yoshitsune and his desire to avenge his father, is also shown in the Noh play Kurama-tengu (“Kurama-tengu (Long-nosed Goblin in Kurama)”). In the play, the Great Tengu represents the figure of Sōjōbō. The Great Tengu says he his impressed with the Ushiwakamaru character, the young Yoshitsune, for his respectfulness and admirable intentions. Not only does he help Ushiwakamaru by training him to become a great warrior and defeat his enemies, he also promises to protect him and support him in future battles.
Sōjōbō