Takeiri was first elected to public office as a Soka Gakkai-endorsed independent candidate in April 1959 as a member of the assembly for Tokyo's Bunkyō Ward. In the early 1960s, Takeiri was an active participant in the formation of the Komeito Political Union, the predecessor to what would later formally become the Komeito political party in 1964, the latter of which would appoint Takeiri to be Deputy General Secretary from the start. Around this time, Takeiri befriended future Prime Minister Kakuei Tanaka, who he would assist in various capacities later on.[3]
Takeiri was elected to the House of Representatives for the first time in 1967, serving as a representative for Tokyo's former 10th ward seat. Following the retirement of Takehisa Tsuji, Takeiri took over as Komeito's leader. In a 1967 interview, Soka Gakkai president Daisaku Ikeda claimed to have himself handpicked and trained Takeiri for the Komeito leadership.[4] In 1970, Takeiri dived into the heavily polluted Tokyo Bay to collect samples for a Komeito-managed environmental survey of bay waters in Tokyo and Osaka.[5] On 21 September 1971, Takeiri was stabbed with a knife in front of Komeito headquarters by a thug and suffered from heavy injuries for the next three months.[6]
Takeiri was intimately involved with Prime Minister Tanaka's plans to normalise relations with the People's Republic of China in the early 1970s, despite Komeito itself not being formally involved in the process. In July 1972, Takeiri flew to Beijing and met Zhou Enlai, and thereafter returned to report back to Tanaka and then-Foreign Minister Masayoshi Ōhira.[7] In addition, Takeiri was also a part of a Komeito delegation to North Korea in that same year, where he met Kim Il Sung.[8]
In 1974, Soka Gakkai and the Japanese Communist Party secretly agreed to a ten-year accord of reconciliation, and, in addition, Kenji Miyamoto and Daisaku Ikeda had held multiple meetings with each other in that year. These interactions came to light in 1975 and sparked internal strife in both parties as many Japanese Communist Party members were atheists that opposed working with religious groups, whereas many Komeito members were religious anti-communists. For this reason, the two groups had refused to cooperate in the past despite both being opposition parties. Further controversy ensued when an alarmed Takeiri claimed to have never been notified of these interactions and expressed criticism of Ikeda. At the Komeito party convention in October of that year, Takeiri attempted to restore the confidence of more anti-communist members who he believed to have lost trust in the party.[9]
At the Komeito national convention in 1978, Takeiri softened Komeito's defense policies by moving it towards the centre by muting opposition to the US-Japan Security Treaty and Japanese Self-Defense Forces.[10] Takeiri warmed his position even further in 1981 by stating that "under the volatile international circumstances, the need for Japan to be responsible for its own security is rising."[11]
Takeiri stepped down as Chairman of Komeito in December 1986 after having served for almost 20 years in that position. Thereafter, he became the party's Chief Advisor instead. He declined to run for the 1990 general elections and retired from politics afterwards, which had set up a precedent within Komeito circles which states that one should retire before turning 66 years old. In 1996, Takeiri was rewarded the First Class Grand Cordon of the Order of the Rising Sun.[12]
