Short introduction: kanji can be read and pronounced in several ways. The different readings are divided into kun-yomi for words that originated in Japan and on-yomi for readings that are based on the Chinese pronunciation. Additionally many kanji have alternative readings when they are used in names. Here I’ve included the common kun-yomi and on-yomi readings of each kanji, but not any of the alternative possible readings that are used for names because they can be numerous.
When I write in English I write the character names first name first. Note that in Japan names are presented the other way around with the first name last(as I’ve done here with the kanji).
Now for the characters!
Kazuki Yasaka: 矢逆 一稀
Kazuki is made out of 一 (hito-, hito.tsu, ichi, itsu) which means “one/ no.1” and 稀 (mare, mabara, ki, ke) meaning “rare/ phenomenal”. These are good positive things that make for a nice name. They also point out that he’s special.
Yasaka is made out of 矢 (ya, shi) which means “dart/ arrow” and 逆 (saka, saka.sa, saka.rau, gyaku, geki) meaning “inverted/ reverse/ opposite”.
Tooi Kuji: 久慈 悠
Tooi consists of 悠 (too.i, haru.ka, yuu) which means “permanence/ distant/ leisure”. Based on the pv his name seems to suit him and his solitary/distant lifestyle. His name also indicates that he’ll be calm and easygoing, or at least that’s what the ones who gave him his name might’ve wanted him to be.
Kuji is made out of 久 (hisa.shii, kyuu, ku) which means “long time/ old story/ eternity/ forever” and 慈 (itsuku.shimu, ji) meaning “mercy”.
Enta Jinnai: 陣内 燕太
Enta is made out of 燕 (tsubame, en) which means “swallow (bird)” and 太 (futo.i, futo.ru, tai, ta) meaning “fat/ plump/ thick”. Note that “fat” is derived from the word for “big/ grand/ great”, so “a great swallow”.
Jinnai is made out of 陣 (jin) which means “camp/ battle formation” and 内 (uchi, nai, dai) meaning “inside/ within/ between/ among/ house/ home/ one’s own”.
Keppi is written in katakana, which are basic characters with sounds but no meaning. Katakana is generally used for lone words and for emphasis (similar to italics). Keppi does not exist as a word in Japanese and is most likely derived from “kappa”, which seems to be what he is?
Leo/Reo Niiboshi: 新星 玲央
Leo/Reo is made out of 玲 (rei, rou) which means “tinkling/ the sound of jewels” and 央 (ou) meaning “center/ middle”. Note that his name is spelled as レオ (Reo) in Japan, but many English speakers prefer to call him Leo instead as it sounds similar, but is easier to pronounce. L/R are generally interchanged between Eng and Jp names for this reason, as there is no L-sound in Japan.
Niiboshi is made out of 新 (atara.shii, nii-, shin) which means “new” and 星 (hoshi, -boshi, sei, shou) meaning “star”. Together the kanji are read as shinsei which means “nova” or a “rising star”.
Mabu Akutsu: 阿久津 真武
Mabu is made out of 真 (ma, makoto, shin) which means “truth/ reality/ genuineness” or “Buddhist sect” and 武 (take, take.shi, bu, mu) meaning “warrior/ military/ martial/ courage/ chivalry/ arms”. This conveys the image of him as a pure and proper “officer”. A “good cop” if you may.
Akutsu is made out of 阿 (omone.ru, kuma, a, o) which means “Africa/ flatter/ pander/ fawn upon/ corner/ recess”, 久 (hisa.shii, kyuu, ku) meaning “long time/ old story/ eternity/ forever” and 津 (tsu, shin) meaning “haven/ port/ harbour/ ferry”. I believe this surname is taken from a place.
Sara is written in katakana and because of that the name doesn’t hold any meaning in itself. However we know that Leo named her after 皿 (sara) which means “plate”, because that’s what they found her on.
One thing that may be worth noting is that many of these names are quite feminine. Some of them can be gender neutral, but most are actually female given names. It might be a reference to typical bl-naming conventions, where the characters have feminine names.
Note for the future:
Sara shares her last name (Azuma) with the red bridge in Asakusa.
Toi’s brother is called Chikai which can be read as “close”.