WaniKani level won’t matter, because the manga uses furigana (kana readings beside the kanji).
The biggest consideration then is how far you are in Genki. Having just started it, you’ll find reading a manga to be extremely difficult, as you won’t know any of the grammar (not to mention if you don’t know much vocabulary).
For me, reading manga and looking up all unknown grammar worked very well. But I also knew a lot of random grammar before going into my first manga in Japanese.
For you, it’ll come down to which of these options sounds better (and viable) to you:
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Wait until you complete Genki I and have started Genki II before you attempt reading a manga.
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Start reading a manga soon, and invest one to two hours every day, seven days a week, into learning the grammar used in it. After about three months of this, you may be able to reduce this to five days a week. (Note that this manga will span two months of reading.)
If you don’t know a lot of vocabulary, you’ll feel like you’re struggling regardless of whether you know the grammar already or not. You simply have to accept that when trying to read a manga early on. (The alternative is to look into graded readers.)