After graduating from Hosei University, Hara worked at Denso, a Toyota Group subsidiary, where he began developing a barcode system. ^{[ 6 ]} In 1992, at Denso’s development department (later Denso Wave), he was tasked with creating a new 2D code to efficiently track automotive components. ^{[ 7 ] [ 8 ] [ 9 ] [ 10 ]} One day during a lunchtime game of go, he realized the black-and-white patterns could encode information. ^{[ 6 ]} He also researched publications to find a unique proportion for the position pattern to ensure readability. ^{[ 11 ]} The code was introduced in 1994. ^{[ 12 ]}

In 2021, QR codes were being used to book and track COVID-19 tests and contact tracing. ^{[ 6 ]} Hara has stated that he would like to develop QR codes for additional medical purposes, including imaging such as x-rays or electrocardiogram data. ^{[ 2 ]} Hara still works for Denso as of 2024. ^{[ 1 ]}

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