Mainline Pokémon games are generally easy to brute-force one’s way through. This you can do even if you set it to a language you can’t even read (let alone understand).
Some considerations:
Kana Mode vs Kanji Mode
Pokémon games let you choose between kana only (no kanji), or with kanji. There’s no furigana option, so if you go with kanji, you’re going all-in. (You can change this setting from the menu.)
Chances are the kanji used will be generally similar to Alpha Sapphire, which I’ve done a kanji analysis for:

(I believe this was based only on dialogue, and does not include PokéDex entries.)
Once you complete WaniKani level 20, you should be able to recognize about 80% of the kanji used. However, some of those kanji will be in words with other kanji you haven’t learned yet.
Grammar
You mentioned you’re early on in N5 grammar, but there’s something very important to know about grammar:
Simply learning grammar won’t get you very far.
In order to get good at understanding grammar when reading, you need to read a lot.
If you don’t read a lot before you start playing Pokémon Sword/Shield, that’d like reading a book on how to play chess, then entering a tournament without ever having played the game. You may know the data on how the pieces move, but you won’t be familiar with all the patterns the pieces tend to become arranged in.
Intensive Reading and Extensive Reading
Reading is hard early on because you don’t know a lot of words, and you aren’t familiar with the grammar yet. Between now and year-end may not be enough time to build up reading skill.
But that’s okay! You can decide to let Pokémon be your first foray into reading.
You’ll find there are two ways you can generally approach reading: intensive and extensive.
With intensive reading, you’re looking up every word and (most importantly) every grammar you don’t know as you come across it. This can result in learning a lot of various grammar, including grammar outside the N5 and N4 areas (which is good!)
With extensive reading, you’re only looking up things now and then when you’re not understanding what’s going on. But if you get a vague idea of what’s happening, you don’t worry about looking up words.
(These are very rough explanations of the two, and there are many different ways to go about them.)
What’s nice with Pokémon is that you can actually use both methods. Maybe in each town, or once for each hour of gameplay, pick one NPC to talk to and intensively look up their dialogue, until you know all the words (even if you forget them soon after) and you’re familiar with the grammar (even if you forget it soon after). Do this long enough, and you’ll start to recognize the same grammar as you’ll see it come up often. (And a lot of common vocabulary words will show up, too.)
Vague Goals and Clear Systems
I recommend keeping your goal vague. But focus on making your systems as clear as possible.
What are systems? They’re tasks you do every day (or so many times a week) to continuously improve yourself (or continuously make progress on a task).
Here are a few systems you may wish to employ on a daily basis:
- Complete all available WaniKani reviews in the morning, afternoon, and at night.
- Only do WaniKani lessons if the number of Apprentice cards is under 100. (Otherwise you might end up with too many reviews.)
- Watch one CureDolly Japanese from Scratch video (with subtitles turned on).
- Complete one battle in Pokémon Sword/Shield. Screenshot every line of dialogue before, during, and after the battle. Then intensively analyze the vocabulary and grammar from the screenshots.
Note that with a system like this, you can start Pokémon today.