Patrick Ryan

USA TODAY

NEW YORK — Shoshanna Shapiro has finally unlocked the mystery of who she is.

"That I'm secretly a Japanese person," says Zosia Mamet, 28, whose Girls character this season takes a marketing job in Tokyo, where she's seen in Sunday's episode of the HBO comedy (10 p.m. ET/PT). Shosh is "a very quirky, specific individual and the way that Japanese culture embraces that makes her feel at ease."

"She's spreading her Japanese wings!" sings Saturday Night Live star Aidy Bryant, 28, who returns as Shosh's American-based boss, Abigail. "If you could really push that song, that'd be great. It's actively been dismissed here."

Mamet quips: "Yeah, Japanese charts are loving it, but it hasn't quite hit here yet."

Now in its fifth season, Girls follows the personal and professional misadventures of four hapless twentysomethings in New York (played by Mamet, Allison Williams, Jemima Kirke and creator Lena Dunham). Toward the end of last season, Dunham and executive producer Jenni Konner told Mamet that they were considering sending Shosh to Japan, after the character's failed attempts at landing a job and reuniting with ex-boyfriend Ray (Alex Karpovsky).

"At that point, it was like, 'Right, but we'd never go to Japan,' " Mamet says. "Next season, it'd be like, 'Oh, no, instead we sent you to Jersey!' " Even at the start of Season 5, "it was unclear if we were actually going to go or if we were going to cheat New York and send someone" to shoot exterior scenes.

They eventually decided to ship Mamet and a small crew to Tokyo, where they filmed for nearly three weeks last summer. Bryant — whose character resurfaces in a larger role later this season — tagged along for the sweaty sojourn.

"It was true friendship, because it's 99% humidity there in the summer," Bryant says. "It's like being inside of a mouth, it's really rough."

Some of their scenes were shot guerrilla-style on bustling Takeshita Street, a food and shopping mecca that Mamet best describes as "Times Square in an alley." Shosh also visits a fetish club with a potential love interest (Hiro Mizushima), and a day spa where she and Abby get fish pedicures, which are exactly as unpleasant as they sound.

"You put your feet into a little fish tank and the fish eat the dead skin," Bryant says, cringing. "When I saw pictures of it, I just assumed they were little sucker fish who'd skim your foot and suck away, but you can feel them chomp."

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Last summer's visit was their first to Asia, although Bryant says, "If I ever do go back, it has to be with Z." Both made sure to buy plenty of mementos before leaving — facial masks, wind-up toys and kimonos, among them — although their Japanese vocabulary is still lacking.

"The only thing I remember is 'Kawaii!' It's like, cute, but it's extra cute," Mamet says.

Adds Bryant: "My favorite and only thing I learned was 'Sumimasen!' which means, 'Excuse me, I'm sorry.' Basically everywhere I went, I was like, 'Sumimasen! I need to go to the bathroom!' "