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- "Ah, few things in nature are as misunderstood as the playful salmonella bacterium. S-Typhi is the little dickens that--"
- — Hiro, mocking Kamal's cooking
Hiroyuki is Kamal Zaman's roommate at a medical school in United States of America, Earth. He is the more humorous of the couple, and he often makes vague innuendos that make others suggest he finds a girlfriend. However, like Kamal, he is rather geeky and needs to read "How to" books to try to understand dating.