What is the best alternative to Learn Japanese: Sensei on iPhone?

LearnEnglish Grammar (UK ed.), S tier, #1 in grammar learning.

Is there a free alternative to Learn Japanese: Sensei?

Yes: LearnEnglish Grammar (UK ed.) (S tier, #1) is free to download, with in-app purchases.

Yes. 5 apps rank above it in grammar learning: LearnEnglish Grammar (UK ed.) (#1), Grammar Fix (#2), ConjuGato: Learn Spanish Verbs (#3) and more.

Learn Japanese: Sensei is D tier, #6 of 6 in grammar learning. Here is everything that competes with it on iPhone, in tier order.

1
LearnEnglish Grammar (UK ed.)Shigher tier
Free + IAP · ★ 4.7 · 40,161 ratings · score 94
Free English grammar practice app with four CEFR-based levels, about 25 grammar topics and 10 activity types.
2
Grammar FixBhigher tier
Free + IAP · ★ 4.8 · 1,822 ratings · score 76
Teaches the 10 most common grammar mistakes, with each one covered in as little as 10 minutes.
3
ConjuGato: Learn Spanish VerbsChigher tier
Free download · ★ 4.9 · 4,198 ratings · score 68
Spanish verb conjugation quiz app with spaced repetition, audio, conjugation tables, and grammar quizzes.
4
IVERBS Irregular VerbsChigher tier
Free + IAP · ★ 4.8 · 3,287 ratings · score 68
IOS app for learning English irregular verbs, with illustrations, native speaker audio, exercises, flash-cards and a.
5
German Verb ConjugatorChigher tier
Free download · ★ 4.8 · 1,954 ratings · score 67
Looks up German verb conjugations across 16 tenses for 2100 verbs, with audio, example sentences and flashcards.

What is the best alternative to Learn Japanese: Sensei on iPhone?: LearnEnglish Grammar (UK ed.), S tier, #1 in grammar learning.
Is there a free alternative to Learn Japanese: Sensei?: Yes: LearnEnglish Grammar (UK ed.) (S tier, #1) is free to download, with in-app purchases.
Does anything rank above Learn Japanese: Sensei?: Yes. 5 apps rank above it in grammar learning: LearnEnglish Grammar (UK ed.) (#1), Grammar Fix (#2), ConjuGato: Learn Spanish Verbs (#3) and more.