The Trek to Yomi is a short 2.5D side scroller game.

Before we start the guide, I would encourage you to play through the first playthrough blind as to 100% the game it will take a minimum of three (3) playthroughs (without save manipulating).

There are only three endings (and a secret one) that can be obtained in each playthrough. To be optimal I would recommend doing your first and blind playthrough on Ronin (hard) difficultly, otherwise, you may have to do a fourth playthrough.

The game isn't too difficult and is quite forgiving making the Trek To Yomi an achievable 100%.

The first playthrough took me five (5) hours and subsequent playthroughs took around three (3) hours.

Rough Estimate Time to 100%: 12 Hours
The estimate is based off three (3) playthroughs. The first being the blind Ronin (Hard) playthrough. The second I would recommend is the one-hit playthrough and the last playthrough on any difficultly of your choosing collecting all the collectables and upgrades.

Anyways, good luck.

Young blood - Kill your first enemy
End of kindergarten - Finish Chapter 1
After the storm - Finish Chapter 2
Dust and ashes - Finish Chapter 3
Fleeting destiny - Finish Chapter 4
Afterlife traveler - Finish Chapter 5
Trek's end? - Finish Chapter 6
Samurai dies twice - Complete the Game

Unbowed, Unbent, Unbroken- Complete the game in Ronin mode.
This is hard mode and many encounters in the game are much more difficult

Unstoppable - Complete the game on Kensei mode.
Kensei mode is unlocked when you complete the game once on any difficulty. This is the one-hit kill and death mode, it will require you to learn the boss patterns to a high degree. I didn't find any significant difficulties with this mode after completing the game on Kensei mode.

Follow your Heart - Choose Yuki at the end of chapter 6 after the boss battle
Follow your mind - Choose Duty at the end of chapter 6 after the boss battle
Follow your blade - Choose Revenge at the end of chapter 6 after the boss battle
Early End - Kill the boss in Chapter 3. This is the secret ending. After you kill the boss you can still continue with the story in chapter 4. I would try to get this achievement with "No, that's not possible..." You will only get one attempt per playthrough at this.

I'll put this spear into... - Kill Sadatame without getting hit in Chapter 2
That woman is a demon! - Kill Aiko Demon without getting hit in Chapter 4
Forgive me, sensei - Kill Sanjuro Demon without getting hit in Chapter 5
Clash in a mirror - Kill Hiroki Demon without getting hit in Chapter 6

No, that's not possible... - Kill Kagerou Shogun without getting hit in Chapter 3.
I would recommend to manually backup the game before attempting this challenge as once you die you will be sent to chapter 4.

Leave no stone unturned - Find all lore collectables
Dedicated Collector - Collect all upgrades

I used this guide to get the achievements:
https://www.youtube.com/watch?v=nA2ZDYJQgs0&list=PLuGZAFj5iqHdhzzTSPsAwZ8zeMtHq9y0R

I recommend being thorough as you cannot level select or NG+ any missing items and will require a new game and to collect every item again.

This will come in handy - Collect your first upgrade.
Men-Kaeshi-Dou - Execute 50 successful counters
Bloodlust - Perform 50 finishers. This is a staple on Ronin difficultly.

Malicious mischief - Kill 10 enemies without using any weapon. These are just environmental kills. This will come through naturally

Big Bertha - Kill 3 enemies at once with the Ozutsu. There will be parts of chapter 4 where there are enemies who are all in a line. I would recommend doing this either in Easy or Kensei.

Untouchable - Complete a whole chapter without dying and using a shrine. Self-explanatory, although I would attempt this on the easiest difficultly in chapter 2. Chapter 1 has a shrine that cannot be avoided.

Thanks for reading through my guide.
Due to technical issues, there are no pictures :)