Short answers, pulled from the story.
Japanophilia is an outside interest in Japanese culture, people, and history that began during the late 1700s. Carl Peter Thunberg cataloged plants in a Japanese garden during this period which marked the start of the phenomenon.
Key historical figures include Philipp Franz von Siebold who brought flora to Europe, Lafcadio Hearn who lived in Japan as an Irish-Greek author, and Jules Brunet who served as a French Army officer. General José Millán-Astray also adopted Bushido principles for the Spanish Legion after translating Inazo Nitobe's work.
Wapanese emerged as a derogatory word in the early 2000s specifically appearing on Urban Dictionary website in 2003. Weeaboo first appeared in a 2005 The Perry Bible Fellowship webcomic before Christopher Poole added a filter to 4chan later that same year.
British writers praised Japan due to declining industrial productivity in their own country while viewing Germany as a threat. Alfred Stead published Great Japan: A Study of National Efficiency in 1906 prompting pundits to look to Japan for lessons on efficiency.
Experts state there is nothing wrong with loving Japanese culture but obnoxious behavior defines the problem of being a weeaboo. A person becomes a weeaboo when they start to be immature and ignorant about the culture they love regardless of merit.