He's wounded and unhappy
Father: 'Wun-Xi! They kicked you out!? Again?'
Soldier: 'Father, I-'
Father: 'This is the 4th shogun who has turned you away! You disgrace our nation! Get out of here!'
<the old man throws a few belongings at his son>
Father: 'This is no longer your home'
<The father slams the door to the house shut. The son, still wearing samurai armor, glinting in the son on one shoulder and caked with mud on the other, looks perplexed. Then angry. Then sad. Then forlorn.
At the tea shoppe next to his house, spectators have been watching. Most grin and are enjoying the conflicts because they're sad bastards, but one generous man approaches the despirited young man and gives him a cup of tea>
Generous man: 'Your father is annoyed because the crops have failed'
Soldier: 'What? Again! But that's the 2nd time! How-'
Generous man: 'We have a dragon that has immigrated into Nippon and is torching the crops. It lives on that mountain yonder.' <he points into the distance>
Generous man: 'If u want your dad to feel better about you, I say take that sword and your strong shoulders, and kill the dragon for us.'
<he turns to the spectators, unhappy a scene isn't being made anymore>
Generous man: 'What say you, villagefolk? Shall we ask this brave soldier to kill the dragon?'
<they all yell drunkenly and toast with tea, despite it being 9 in the morning>
<The young man begins to trek towards the mountain to kill the Dragon and get in his father's good graces again>