Back round the year 1972, diplomatic relations between the 2 countries normalized and for several years China acted favourably towards Japan, encouragaing the importation of Japanese product, TV, and music.
However, things gave the impression to have turned bitter once more following the increase of Jian Zemin as head of state. Jian grew up in an exceedingly time of Japanese occupation and has obligatory anti-Japan sentiment upon the state, pushing for anti-Japanese education and otherwise.
And I think this is the reason why Japan lose respect for China and break their relationship again.
