Hachiman said to be the same as Ōjin
Summary of Hachiman
In the present form of Shinto, Hachiman is the divine spirit of Emperor Ōjin. Emperor Kinmei (欽明天皇, Kinmei-tennō) in his Regnal Year 32 (571 AD) decreed that the deified Emperor Ōjin was revealed for the first time in the land of Usa (宇佐の地)—the present-day city of Usa, in Oita Prefecture—where he became the patron deity of this city, along with a lesser Shinto female deity called Himegami (比売神) and the Emperor's mother, Empress Jingū.  This trio, known as Hachiman Mikami (八幡三神) is enshrined there. 
Amongst the Hachiman Mikami, there are many shrines that enshrines other figures apart from the trio, like Emperor Chūai (仲哀天皇, Chūai-tennō) instead of Empress Jingū, the legendary hero and Shinto deity Takenouchi no Sukune or Takeshiuchi no Sukune (武内宿禰) and the female deity Tamayori-hime (玉依毘売命 or 玉依姫尊), where there is a dedicated prayer for safe childbirth in the Shinto shrine of Umi Hachimangū (宇美八幡宮) in Umi, Fukuoka prefecture.
Himegami
The three Munakata goddesses (宗像三女神 Munakata Sanjoshin) born from the divination ritual Ukehi or Ukei (宇気比, 誓約, 祈, 誓, 誓占, lit. "pledge divination") between the goddess Amaterasu and the god Susanoo - that is Tagitsu-hime (多岐津姫命), Ichikishima-hime (市杵嶋姫命) and Tagairi-hime (多紀理姫命) - is said where they descended from the heavens as the "Three Pillars of Usanoshima (宇佐嶋) of the ancient province of Tsukushi (筑紫)", located in a temple complex on Mt. Omotosan (御許山) in Usa. 
The Munakata goddesses are thereby the matriarchs of an ancient tribe and clan Munakata-shi (宗像氏, 宗形氏) which fishermen worshipped collectively as a whole. It is thought that the worship of Munakata goddesses by the Munakata clan was due to Empress Jingū's success in the "Conquest of the Three Kingdoms (of Korea)" (三韓征伐 Sankan Seipatsu). Therefore, they are old Shinto folk deities (地主神 jinushigami) before the presence of Hachiman. 
Himegami (比売神) is thought to be the consort or aunt of Hachiman, whereas Tamayori-hime (玉依毘売命 or 玉依姫尊) possibly and perhaps as the mother viewed by opinion aforementioned. Since the description of Hachiman as the Emperor Ojin appeared in the "Digest Record of Todai-ji Temple (東大寺要録 Tōdai-ji Yoroku)" and "Records of the Age of the Gods from the Sumiyoshi Grand Shrine (住吉大社神代記 Sumiyoshi-Taisha Jindaiki), the practice of merging Emperor Ōjin into Hachiman is estimated to have begun in the Nara Period or the Heian Period. 
There are also different theories and opinions concerning the goddesses Amaterasu and Kukuri-hime (菊理媛神 or 菊理媛命, a Shinto goddess venerated as Shirayama-hime (白山比咩), in which both called the goddess Himegami Himiko (卑弥呼, or Pimiko, also known as Shin-gi Wa-ō (親魏倭王, "Ruler of Wa, Friend of Wei"), a shamaness-queen of Yamatai-koku in Wakoku (倭国) around c. 170–248 AD.
Empress Jingū
Emperor Ojin was already destined to ascend the throne from the moment in the womb of his mother and Empress, is called "Emperor in the Womb", is based and interpreted sometimes in her belief as being the "mother deity" to the child-to-be who would be deified. The Three Munakata Goddesses, the Three Sumiyoshi Gods (住吉三神 Sumiyoshi Sanjin) and the goddess Amaterasu who were revered by the tribal clan Munakata-shi due to their aid in the "Conquest of the Three Kingdoms (of Korea)" is also worshiped in various places. It is said by tradition in commemoration after the conquest, Empress Jingu set up eight big military flags on Tsushima (対馬) which then became the origin of the name "Hirohatano Yahata Ōkami (広幡乃八幡大神)", also the origin of the name "Yahata (八幡)" to the Empress' son, the then-emperor Ojin.