阿万音 鈴羽

Amane Suzuha works part-time for the landlord of Rintarou's flat and is on a search for her father in Akihabara. She enjoys riding her bicycle and appears to be at odds with Kurisu.

She is in fact a Time Traveller from 2036 who, using the guise of John *****, seeks to prevent SERN from creating a Time Machine that will lead to dystopia. Though she is unaware of it, she is the daughter of Hashida Itaru./

From Wiki