Through his history, Matarajin was identified with a large number of other figures. Identification between him and
Mahakala, most likely based on the similarity between their names, is known from multiple sources. The process of
Hindu devas acquiring new identities first in
Indian Buddhism and subsequently in
East Asian Buddhism is well documented. A deity worshiped near the Eastern Pagoda on
Mount Hiei, Ina Tenjin (移那天神), was historically identified as Matarajin and as a manifestation of Mahakala. According to the writings of the Tendai monk Kōshū (1276-1350), Matarajin was regarded as either identical with Mahakala or as one of the demonic
dakinis accompanying him, and was believed to devour livers. This was considered to be a way to help those negatively impacted by heavy
karma with reaching a pure land faster, similarly as in the case of analogous beliefs about other dakinis. Most likely this tradition depended on the Chinese monk
Yi Xing's description of dakinis, known from his commentary on the
Mahavairocana Sutra from 725.
Dakiniten and Matarajin could be associated with each other, though their conflation is better attested in
Shingon than
Tendai, and in the latter the two were only linked by the
Kurodani branch. A text dated to 1361 identifies Matarajin with Dakiniten as a deity fulfilling wishes. A stone said to resemble a white fox located near the main hall of Enryaku-ji is referred to as Matara Tenjin in various documents, despite being associated with Dakiniten. The Edo period work Reflections on Inari Shrine (稲荷神社考,
Inari jinja kō) lists both Matarajin and Dakiniten among names which could be assigned to fox spirits, alongside , Yashajin and Fuku daijin. It states that "a three-faced and six armed deity is the true form of these Matarajin and wild foxes". A network of connections leading to exchange of attributes existed between Matarajin,
Shinra Myōjin (新羅明神) and
Sekizan Myōjin (赤山明神) The latter two were originally regarded as protectors of two rival branches of Tendai. Shinra Myōjin was associated with the
Jimon tradition, while Sekizan Myōjin with
Sanmon, with the former centered on
Mii-dera and the latter on
Mount Hiei. Despite the connection between them, Matarajin never acquired the title of
myōjin (明神; "bright deity") himself. Through his association with Sekizan Myōjin, Matarajin also developed a connection to . The latter was conflated to him as a god of destiny, though in origin he was a
Daoist figure comparable to Buddhist
Enma. As Sekizan Myōjin's name was derived from the name of a mountain, Sekizan (Chishan in
Shandong), the link might have originally relied on both of them being Chinese
mountain gods of similar character. A further deity who could be identified with Matarajin was
Susanoo, possibly due to analogies between the latter and Shinra Myōjin. This tradition is documented in a text from
Gakuen-ji, which states that after being buried there Susanoo came to be worshiped under the name Matarajin, as well as in sources compiled by adherents of the Sanmon tradition on Mount Hiei and from Hinomisaki, a branch shrine of
Izumo-taisha. Additionally,
Jimon denki horoku, dated to the
Muromachi period, states that "Susanoo has many traces, among them Matarajin and Gozu Tennō in India, the god of
Mount Song in China, and the great
Silla deity (Shinra Taijin) in Japan".
Sange yōryakki explains that "Susanoo, who is also called Matarajin" enabled
Saichō to return safely from his journey to China because he prayed to this deity. In
Nihon Shoki kikigaki, a commentary on the
Nihon Shoki, listed Matarajin, but also Shinra Myōjin,
Banko,
Yama, and
Kōjin as figures identified with Susanoo. Matarajin and Kōjin could be identified with each other as well, for example as deities associated with causing obstacles. In the
Kōjin saimon, the eponymous deity is said to be "fundamentally existing, born-at-the-same-time Matarajin". As an extension of his link with Susanoo, Matarajin also developed a similar connection with the epidemic deity
Gozu Tennō. In addition to the conflation of the two, in one of the reinterpretations of the cycle of myths focused on Susanoo, Matarajin and a horde of demons under his command assist him when he attacks
Amaterasu. During the Muromachi period, Matarajin came to be merged with Okina (翁), a figure originating in
sarugaku and
noh performances. The word okina means old man, but in the context of these performing arts it designates a specific mask, play and deity. Okina might be identical with Shukujin understood as a singular deity rather than a category, as indicated by
Konparu Zenchiku in his work
Meishuku shū (明宿集), in which he envisioned a complex network of connections between various
shukujin, regarding all of them as manifestations of a single figure. He does not directly mention Matarajin among them, though it is nonetheless sometimes assumed that he might be implicitly referenced in a cited tale about the origin of sarugaku. It has also been pointed out that both Matarajin and another figure linked to
shukujin,
Hata no Kawakatsu, are associated with the
Kōryū-ji temple in
Kyoto. Matarajin could also be regarded as a manifestation of
Amida Buddha, specifically of his "wheel-commanding body" ( 教令輪身,
kyōryōrinshin), a term which in the nomenclature of esoteric Buddhism designates the wrathful aspect of a
buddha. This idea might have initially developed because the latter was the central object of worship in the so-called "constantly walking
samādhi", while the former was enshrined as the protector of the halls it was practiced in. According to
Eison, the founder of the
Shingon Ritsu, Matarajin had the face of
Mañjuśrī; in later tradition influenced by his teachings the two deities could outright be identified with each other. As an extension of the link between Matarajin and Mañjuśrī, the
okina mask could serve as the symbol of the latter from the middle of the
Kamakura period onward. ==Iconography==