Watch Yozakura Quartet: Hoshi no Umi Online

"Tsuki ni Naku" will take the story content from volume 11 of the manga, which features a visit to a onsen by the members of the Hiizumi Life Councelling Office, while the town's police force have to deal with a new youkai-hunter threat. This OVA is bundled with the limited edition of the manga (14th, 15th, and 16th).

An OVA based on the Hoshi no Umi arc of the manga spanning chapters 26-34. This arc focuses on Rin Azuma, a Jiang-Shi yokai resident of Sakurashin adjusting to her new life in the city and working for a ramen shop. One day her former friend Zakuro Kurumaki invades Sakurashin to capture Rin and convince her to join her in destroying the city with the other yokai hunters as well as Enjin Hiizumi, the main antagonist of the series. Akina Hiizumi and the other members of the Hiizumi Life Counseling Office take action to save Rin, 'tune' the yokai controlling Zakuro and protect the city. (Source: ANN)

Hundreds of years ago, the borders between the worlds of humans and youkai temporarily overlapped, resulting in many residents of both crossing over to the other side. In the years since this event, the city of Sakurashin has become a central hub for all inter-dimensional affairs—a result of both the sacred Seven Pillars around the city serving as a beacon for the youkai, and the efforts of the Hiizumi Life Counseling Office in keeping the townsfolk happy. This office is composed of Hime Yarizakura, the young mayor of the city; satori Ao Nanami, who can read people's minds; half-youkai Kotoha Isone, who can summon anything by speaking a word; oni siblings, Kyousuke and Touka Kishi; and the office director Akina Hiizumi, who inherited his family's ability to force youkai back to their world. Besides volunteer and arbitration work, the Life Counseling Office also suppresses any Strikes: rare occurrences where humans are suddenly infused with youkai powers and go on a rampage. But the appearance of a sinister man signals trouble as Strikes become increasingly common, political rivals make their moves, and malicious individuals descend upon the city. As the self-appointed defenders of Sakurashin, it's up to the Life Counseling Office to protect the idyllic city they call home! [Written by MAL Rewrite]

The world of Yozakura Quartet is actually not one, but two worlds: one of humans, and one of youkai. Despite appearing mostly human, youkai may have animal like physical traits, along with a number of special abilities. Normally youkai are confined to their world, but some have found their way into the realm of humanity. As a symbol of peace, and a bridge between the two realms, a city was constructed within the protective barrier of seven magical trees, otherwise known as the Seven Pillars. This city of Sakurashin is home to both humans and youkai, with the peace between them maintained by the Hizumi Life Counseling Office. The director of this office is Akina Hiizumi, a teenager with the inherited family ability to perform “tuning,” which can send harmful youkai back to their world permanently. He is aided by a group of girls, including the town’s 16 year old youkai mayor, Hime Yarizakura, their town’s announcer and resident telepath, Ao Nanami, and Kotoha Isone, a half-youkai who can summon objects just by stating the object’s name. As new residents enter and mysterious events begin to take place, this quartet of protectors and their closest friends must continue to guard the city of Sakurashin, and maintain the fragile balance of peace between humans and youkai.