update cover image; simple version
update cover image; simple version

kmuto/review,masawada/review,kuad9/review_study,krororo/review,kuad9/review_study,orangain/review,krororo/review,kmuto/review,takahashim/review,murashitas/review,takahashim/review,suzuki/review,suzuki/review,masawada/review,orangain/review,murashitas/review,kmuto/review,krororo/review