NEW DELHI, July 2 -- When Japan's Prime Minister Sanae Takaichi arrived at Hyderabad House on Thursday, she carried a list. By the time she left, 150 Japanese companies had signed memoranda of understanding committing a combined $12.5 billion to India through 120 deals, the largest single-session commercial commitment from Japan to an Asian partner in recent years.

The figure, confirmed by multiple sources familiar with the summit proceedings, caps a period in which India and Japan have moved steadily from strategic alignment to commercial integration. Takaichi, whom Prime Minister Narendra Modi described as his "younger sister" at the end of their joint statement, arrived for her first official India visit as Japan's head of government....