Ichinomiya means "first-ranked shrine", and each province had their own, as well as Ninomiya (second ranked), Sannomiya (third ranked), etc. This is the Ichinomiya for what was Awa Province, now Tokushima.
It is also the site of what was the 13th temple on the Shikoku 88 temple pilgrimage. There used to be a temple in the grounds called Ichinomiya-Ji, and pilgrims worshipped at both the shrine and the temple. The temple was destroyed in early Meiji but later rebuilt just across the road and renamed Dainichiji.
The main enshrined kami is Ogetsuhime, a goddess that approximates an "Earth Mother". According to the Kojiki, Susano asked her for some food and she produced it for him out of her various orifices. Feeling the food was therefore "impure" he killed her and scattered her body and from the various parts the foods of Japan, rice, millet, beans etc, grew. This is such an archetypal myth that it is not surprising that similar myths exist in other parts of Japan, though with different names. What is most interesting is that Ogetsuhime is the ancient "divine" name for Awa.
The second enshrined deity is Amenoiwatowake, one of the kami from Takamagahara, the "High Plain of Heaven" who escorted Ninigi in his descent to Japan. She is enshrined at Kashihara, the "palace" of Jimmu in Yamato.
What these 2 kami suggest to me is that as the Yamato fought their way east from Kyushu they appropiaited the kami of the peoples they conquered and incorporated these kami into their own mythology to justify their divine right to rule.
There are many secondary shrines within the grounds, but no signboard so cannot say which other kami are enshrined here.