This last WoG destroyes the sword+stairs option, since it isn't possible due to the layout. That leaves mainly options 1. Run, 2. Sword, and 3. Upstairs+Knife.
Much has already been said, but I'll add some things not mentioned already:
- Mother is an advantage that hasn't been mentioned enough. Option 2 is essentially a 2 vs 1, because due to the placement of the sword, Tokei will think that we are running away and won't take the time to knock out our mother. She will have time to come to our help, if Tokei hesitates even a bit when he sees us holding a sword. Mother will give us a crucial half of a second, when Tokei focuses on her instead of the swordpoint.
- Vesvious implied earlier that our difficulties with swords come mainly from our lack of skill, not just lack of physique. As such, we should not think of us as a 5 year old of our world, but as a very short unskilled and weaker combatant. We can't win a fair duel, but the matchup is not as lopsided as it would be in real life. This assumption does rely on Tokei not being a particularly powerful Samurai, but hey, if he is, he we are dead anyways.
- "Evasive maneuvers" is total crap, Tokei isn't some oversized RPG boss who will run past us if we juke with our chubby feet. Tokei is a vastly superior athlete, our only advantage in running away is our headstart.
- Our height difference is an advantage to us in any surprise attack. Tokei's automatic counters will be unusable due to our weird vector of attack. This will help us in options 2 and 3.
Even with all that said, running away might still be the best option. It is however solely dependant on how close helpful ninjas are to our house. We won't have long before Tokei will catch us, since he is likely to be much faster. I would be okay with running away here.
Still, I will paint a more combative scenario here for those disinclined to leg it:
[X] Grab the sword and look menacing. Tokei will hopefully pause in the hallway to assess you as a threat, since he doesn't have to chase you anymore. Wait for the exact moment when mother tackles Tokei from behind, and try to run through Tokei. After that, run away and scream for help.