At the next place Mr. MacDuckston took me to, Basanova, in a not very exciting neighborhood a few train stops west of Shibuya, the broth was definitely the star. That’s because Basanova specialized in green curry ramen, a clever adaptation of Thai flavors to Japanese tastes. It was fascinating to slurp, at once vibrant with the heat of chilies and the aromas of lemon grass and kaffir lime, but at heart a classic Japanese ramen. You won’t find this in Bangkok.

LIKE Nagi, Basanova was a nice place to relax. Sure, there was a ticket vending machine, and you ate at a stainless-steel counter, but the atmosphere invited lingering with a beer or two, and the owner didn’t mind our taking plenty of pictures. He even came over to chat, explaining that because his parents came from opposite ends of Japan — hence from vastly different ramen traditions — taking the fusion-cuisine route was a natural decision.

As we left, Mr. MacDuckston and I were followed out the door by a young woman who’d been eyeing us curiously. In the street, she identified herself as Kana Nagashima, a student just returned from a decade in Singapore who had started a ramen club at her university. Her giggly enthusiasm was delightful, and she seemed as impressed with us as we were with her. Before we moved on, she and Mr. MacDuckston exchanged contact information. Talk about meeting cute.

Another fusion dynamic was at play even farther west, at an unassuming corner shop called Ivan Ramen. Ivan is the brainchild of Ivan Orkin, a 46-year-old New York City native and former cook at Lutèce who in 2003 moved to Tokyo with his Japanese wife and son and, well, needed a job. Since “ramen’s fun,” as he told me one morning before the shop opened, his path was set. He started Ivan Ramen in 2007, and despite occasional skepticism from traditionalists it became a hit. His classics — salt and soy broths of remarkable single-mindedness — and his whimsies, like a “taco” ramen or rye-flour tsukemen (noodles served dry with broth for dipping), are so popular that he has a line of dried products in Circle K convenience stores and a line of 20-odd customers outside his door.

“One of the reasons it’s an obsession is it’s truly an everyperson’s dish,” Mr. Orkin said. “Pricewise, it’s affordable for just about anybody. It comes in a bowl, and a good bowl of ramen is balanced perfectly: the soup, the noodles, the toppings, everything works together. So when you’re eating it, even though it’s all these disparate ingredients together, somehow they feel as if you’re eating one thing.”

Nowhere did I have a more balanced bowl than at Ikaruga, where I ate with Meter Chen, a fashionable Hong Kong transplant who works in the entertainment industry and who has written a Chinese-language book about ramen, and his assistant, Naoko Yokoi. As we stood in a 20-minute line out front, Mr. Chen was hopeful — he liked Ikaruga’s logo. “You know if the taste is good or not,” he said later, by the attention the owners pay to design.