A lot of people recommend graded readers for transitioning to native material. These are stories / books specifically made for learners of Japanese and they increase in difficulty depending on the level. You can find a great post about it here:
Personally, I’ve only had the level 1 graded readers by Ask before transitioning to actual books written for a Japanese audience. There are several book clubs you can find here on the forum - you can either join them and participate in the discussions, or just use them to find books that might suit you. That’s how I got my first “real” Japanese book, 魔女の宅急便 (Kiki’s Delivery Service). The book clubs are split into different categories, so you can find books for absolute beginners, beginners, intermediate and advanced learners.
There’s not really anything catered towards your WaniKani level, though. No matter what kind of book you’re reading (or any other kind of media you consume), you’re always going to encounter stuff you don’t know yet. A first instinct might be to think that you still need to learn more before trying native media out again, but the truth is that you’re never going to be ready this way. And of course language is not just words, but you also need grammar to understand something. And as grammar is not a part of WaniKani, it makes it harder to really recommend something based on WK level alone