YANGON, Myanmar — On a street in central Yangon, the final moments of Kenji Nagai’s life were captured in a Pulitzer Prize-winning photograph, an image that exemplified the brutality of military rule in Myanmar. Mr. Nagai, a Japanese journalist, was shot five years ago during a crackdown on protesters by security forces, and his death was a low point in relations between Myanmar and Japan.

Now, as Myanmar seeks to shed its authoritarian past, a much different picture is emerging. Japan is rapidly ramping up its presence in the country with a heavyweight deployment of government assistance and corporate investment that is challenging China’s dominant position in Myanmar.

One block away from the spot where Mr. Nagai was killed, on the fourth floor of City Hall, two dozen Japanese engineers are drawing up a master plan to remake the roads, telephone and Internet networks, and water supply and sewage systems of Yangon, the country’s long-neglected commercial capital.

“Myanmar is saying, ‘Welcome! Please help us,’ ” said Ichiro Maruyama, the deputy chief of mission at the Japanese Embassy in Yangon.