This is just a supplementary guide for studying Japanese on iOS, you should refer to other sources for general knowledge like the order of things to study, textbooks, etc. Go to /r/LearnJapanese, DJT site, Learning Japanese with Anonymous, Step by Step Guide for learning 日本語 and google for more information.

I. Spaced repetition

Anki is the obvious choice. There are tons of user-created decks and you can sync your decks and progress across devices.

Although a lot of apps mentioned in this guide have built-in flashcards feature.

II. Guides / Textbooks

Tae Kim’s Guide to Learning Japanese — beginner’s choice.

Human Japanese | HD—great interactive textbook. It features cultural reference, audio, games and quizzes; the writing is very informal. Intermediate edition is also available.

III. Studying Kana and Kanji

Dr. Moku’s Hiragana Mnemonics and Dr. Moku’s Katakana Mnemonics. Quite funny mnemonics for recognizing the characters, has stroke order and pronunciation.

iKana touch — Hiragana and Katakana study tool—fancy design, has recognition and writing tests.

Don’t forget to check out iKanji touch — Japanese Kanji Study Tool after you’ve successfully learned Kana.

KanjiBox—bad design, in-app purchases for components. Quite functional. And people seem to like it. Maybe it’s your thing too. Online version available here, requires registration.

Remembering the Kanji—companion app for Heisig’s books.

IV. Dictionaries

Japanese

Midori

Tangorin — offline version for the website.

imiwa? (free)

wishoTouch—obviously a dictionary with emphasis on handwriting. OCR module available for purchase.

大辞林—Jp­-Jp dictionary.

広辞苑第六版 — 動画・画像・音声付き—another Jp­-Jp dictionary with inferior interface. Not available at the US AppStore.

EBPocket Professional—dictionary viewer for EPWING format (it’s used for Jp-Jp dictionaries). There are two other viewers on the AppStore but they’re outdated.

V. Readers

i文庫HD—probably the best one, but I didn’t have enough time to study it yet. JP AppStore only.

Wakaru—not the best app by any means, but it has its perks. It supports dictionaries that are installed on your device so you can select the word in a book and switch to the chosen dictionary to look it up instantly. Even though you can enable all the dictionaries you have in the settings, only 4 are available during reading. What a bummer. You can download thousands of books from the app (Aozora and Hosizora Bunko), they are free and sorted by level.

VReader—probably not worth mentioning but it comes with built-in dictionaries and some great books from basic fairy tales to Haruki Murakami.

VI. Various

GoodReader—it has the best PDF engine IMO. I might be wrong, but I’ve been using it for ages and it’s fast and snappy.

Tweet at me if you have an addition or a correction.