Best for: Looking up exactly how a grammar point works
Three-volume grammar reference published by The Japan Times. Each entry explains one grammar point in depth, with many example sentences, notes on usage and related expressions.
JLPT prep book series from ASK Publishing, split by level and by skill: grammar, vocabulary, kanji, reading and listening. Each book is a week-by-week plan with one short lesson per day, with English, Chinese and Korean translations for self-study.
YouTube channel with hundreds of free Japanese lessons, best known for a series that walks through every chapter of the Genki textbooks, explaining the grammar and building practice sentences. Relaxed and funny enough to listen to on the go. His website, tokiniandy.com, adds paid companion courses with exercises and tests for Genki and Quartet.
Grammar study tool that teaches points by JLPT level and reviews them with fill-in-the-blank sentences on a spaced repetition schedule.
