Ghost of Tsushima works a little different to many other action-RPG open-world games. There are no real levels, and you can technically take on any enemy right from the start of the game. The main thing you will be missing is an arsenal of tricks, techniques, and equipment that you can unlock as you level up, giving you an edge against certain types of enemies.
You don’t really have a level the way you do in similar games, and instead you gain access to new techniques and skills by completing Tales. Finishing Tales will earn you Skill Points that can then be spent on your various Techniques, improving Jin’s abilities as a Samurai, and as a Ghost.
Your weapons will be upgraded through blacksmiths and weaponsmiths, not by killing. You don’t even earn experience from killing enemies the way you do in many other games, as this would be very punishing for anyone who chooses to try and play out Tales using stealthy options where they can.
Instead, it allows you to play through the different Tales however you see fit and get the same advancement at the end of the quest. By completing Tales, you are helping the people of your island, destroying the efforts of the Mongol invaders, and growing your legend. This makes finishing side quests just as important as finishing missions when it comes to leveling up your character.
As your Legend grows, you will also earn Technique Points that can be used to increase your skills within certain stances, making you fierce fighter. You will need to make decisions about what to spend your Technique points on, and splitting the points between advancing in your Stances, and learning new Techniques.