Migaku is a series of tools to make language learning easier, all bundled into one convenient monthly subscription. Originally born out of some developers working on Anki extensions for Japanese language learners, Migaku has grown into a comprehensive set of tools that all work in conjunction to help increase your ability to immerse in Japanese language content. Centered around a browser extension, Migaku (which means "to polish") acts more like a support app on top of your browser. It has a number of different features, from enabling convenient subtitles with easy lookup and Anki card creation across a wide range of sites such as Netflix and YouTube, a custom dictionary app, and a reader app to make parsing Japanese text easier, among others. Everything is designed to facilitate immersion learning, by not only helping you parse whatever content you're engaging with, but also making it easy to create effective flashcards in Anki using the content you're looking at without having to mess around in settings too much.
Migaku is pretty useful now, but it's still a work in progress, and as such has a few rough edges. Though on the other hand, it's being improved all the time, and new features are added regularly. If you're a Japanese learner who wants to immerse yourself more or begin sentence mining with Anki, Migaku is a valuable tool to make it easy.