A mother boar raised Inosuke Hashibira ever since he was young and thrown to safety into water by his mother shortly before she died. Whilst he did live in the mountains by himself he still managed to learn how to talk by learning from other humans.
These humans were Takaharu and his elderly grandfather. One day as Takaharu returned from work he found his grandfather sitting on the porch and feeding a strange animal who had a boar head but the body of a baby wearing a diaper, this was Inosuke though Takaharu wasn't aware he was human. Takaharu yelled at his grandfather not to feed strange animals and swiped at the young child with his hoe. As he had a terrible upbringing Takaharu had a very foul mouth but still cared for his grandfather all by himself, especially now that the old man's memory had begun failing him. He told his grandfather not to feed Inosuke as his mother could come down from the mountains in search of it and he non-committally agreed.
Another time, when Takaharu returned home he saw Inosuke there again sitting happily in his grandfather's lap as the old man read to him from a book of poetry called The Hundred Poets. Takaharu yells again and chases Inosuke off, returning to his grandfather he tells the man not to spoil the boy like his own grandchild and even if he is feeling lonely he cannot allow the child to stay near them as his grandfather once again agrees.
Sometime after this incident Takaharu once again returned to see Inosuke with his grandfather as the old man reads the cloth attached to boy's diaper and reads from it to tell him his name, Inosuke Hashibira. He tells the boy that it must be his name given to him by his parents and to take good care of it. Mortified, Takaharu yet again yells at his grandfather for indulging the child and attempts to shoo Inosuke away. However, this time instead of running Inosuke kicks Takaharu in the face and tells "Takosuke" to shut up and bring him his usual baked mochi and that this was his turf now. Takaharu reluctantly obliges and Inosuke laughs as he eats the mochi while in his grandfather's lap.