authentic japanese + rapid reading japanese is the next (and almost last) step. Don't give up on textbook learning yet, tobira is not enough to jump into the native material world while authentic japanese is.Tobira teaches you how to understand japanese for real in specific situations but you get lost easily when rules are broken, Authentic japanese teaches you how to understand japanese for real even when the japanese used stray away from what you've learned. it's the book you need to finally dive into native material and stop worrying about textbook learning (even though doing kanzen master n1 wouldn't hurt)
i recommend you to take the audio course too to level up your listening level the same way and rapid reading to be able to read like a japanese, yes because apparently, foreigners and japanese people don't read the same way (we read word per word which is supposedly a terrible and inefficient way of reading japanese while japanese read more "globally" and, i think, form gradually a picture in their head, kinda weird to explain). the title is misleading though, the goal is to understand better what you read without struggling, which also results in reading faster. This is not a textbook per sey, it's really a complementary book to authentic japanese that teaches you how to read like a japanese and gives you techniques + tools to read better long texts. they even advertise each other on their covers