Even as the friendship between Shinzo Abe and Narendra Modi blossomed during the new Indian leader's first foreign trip, Japan Inc refused to get misty-eyed, wary of the pitfalls of doing business on the sub-continent.

A five-day tour that began with a bear hug and a day of sightseeing in the ancient Japanese capital of Kyoto worked itself up through a crescendo of mutual compliments that culminated in Tokyo's pledge to spend USD 34 billion in India over the next five years.

Companies love the idea of India, with its huge untapped market and its vast, cheap workforce. But they know there are potential problems; Japanese suitors have stumbled more than once before.

"India's very weak infrastructure adds to the cost of making and moving things there," said Takashi Kodama, head of Asian economic research at Daiwa Institute of Research.

"Unless you resolve that, the current hopes for India that the world has cannot spark an investment boom," he said. On top of dodgy roads, ramshackle railways and other weak infrastructure, there are complex local customs for multi-national firms looking for somewhere other than China to set up shop.