単語木 - TOEIC・英検の英単語学習 is an education app by devsky2016.Inc with 5,000+ downloads (about 8.8K estimated). +11 installs in the last 7 days. Released Oct 27, 2017. Install growth, rank history, SDKs and ad networks.
From the store listing: “Learn and review English vocabulary efficiently using the forgetting curve. Create your own personalized vocabulary list! Ideal for TOEIC, Eiken (English proficiency test), and university entrance exam preparation.”