In 1958, Founder Niwano declared his intention to move actively into a new phase in which the true purpose of Rissho Kosei-kai would become clearer. The first step was the affirmation that the main focus of devotion for all members is the Great Benevolent Teacher and Lord, Shakyamuni, the Eternal Buddha.

Other important steps were undertaken at the same time. First, because the founder considered education so vital, he realized that the way to make the truth apparent to others was for each member to study the Lotus Sutra thoroughly and to apply its teachings in practical ways in all phases of their daily lives. To create a nationwide pool of energy for the application of the teachings in society at large, Founder Niwano revised the organizational structure of the branches to make them responsible to a local dissemination center.

In 1960 it was announced that Founder Niwano's eldest son, Nichiko, would succeed him as president. The decision to follow Japanese tradition and make the presidency hereditary was made by the Board of Trustees in accordance with Rissho Kosei-kai regulations.

In 1964, following eight years of construction, the Great Sacred Hall was completed as part of the headquarters complex in Tokyo and was formally opened as the main center for religious activities. A special image of the Eternal Buddha, as described in the Lotus Sutra, was enshrined there. The occasion was one that the founder and all members had long anticipated.

Six years later, Rissho Kosei-kai celebrated the completion of another facility in the headquarters complex, Fumon Hall. Fumon means "the gate open to all people." The hall is intended to be both a place that welcomes all regardless of race or creed and a site at which members can share fellowship and mutual experiences related to their faith.

The completion of Fumon Hall also symbolized a new direction for Rissho Kosei-kai. Starting from the late 1960s, increasing amounts of time, money, and effort have been devoted to the improvement of local communities, to interreligious cooperation, and to activities to promote world peace.

From Founder Niwano's first encounter with the Lotus Sutra, he had held that all religions spring from the same root. He felt that interreligious cooperation is possible if believers are enlightened to the universal truths of their own faith while respecting the beliefs and rituals of other religions.

As a first step toward promoting interreligious cooperation, the founder helped to establish Shinshuren (Federation of New Religious Organizations of Japan) in 1957. The following year Shinshuren became affiliated with the Japan Religions League. This was a landmark event in the early days of the ecumenical movement, when many established religions were less than friendly to new ones.

In 1965 Founder Niwano was the only non-Christian invited by Pope Paul VI to attend as a special guest the Second Vatican Council. The pope expressed his appreciation for the founder's efforts for interreligious cooperation, saying, "It is important for people of religion not to cling to factions or denominations, but to recognize one another and pray for one another." The pope's words reinforced the founder's determination to become a bridge between people of all faiths.

When the founder took part in the Peace Delegation of Religious Leaders for Banning Nuclear Weapons in 1963, he became acquainted with North American Unitarians. Ties between that group and Rissho Kosei-kai were strengthened when the late Dr. Dana McLean Greeley, then president of the Unitarian Universalist Association of America, visited Rissho Kosei-kai after attending the Japanese-American Inter-Religious Consultation on Peace in Kyoto in 1968. Dr. Greeley and Founder Niwano saw eye to eye in their strong desire to further interfaith dialogue. Unitarians have long cherished the goal of interfaith cooperation, and it was they who organized the International Association for Religious Freedom (IARF) in 1900. The meeting of Dr. Greeley and Founder Niwano led to the latter's being invited to the 1969 IARF Congress in Boston, which voted unanimously to welcome Rissho Kosei-kai as a member.

Liberal American religious leaders first conceived of a world religionists' conference for peace in the early 1960s. After several preparatory interreligious meetings, in which Founder Niwano was actively involved, the project came closer to fruition with the founding of the World Conference on Religion and Peace (WCRP) that eventually was to draw the participation of all of the world's major religious organizations. In 1969 Founder Niwano became chairman of the Japan Religions League's Committee for International Affairs, which in 1970 sponsored the first General Assembly of the WCRP, held in Kyoto. Some three hundred representatives of the world's leading religions from 39 nations discussed three major issues--disarmament, development, and human rights --and called for an end to the war then raging in Vietnam. Since that time, the WCRP has held general assemblies in Belgium, the United States, Kenya, Australia, Italy, and Jordan.
As a WCRP representative, Founder Niwano addressed the first Special Session of the United Nations General Assembly Devoted to Disarmament (SSD I) in 1978. He urged the leaders of the superpowers to work for general and complete disarmament, saying, "Instead of taking risks with arms, please take major risks for peace and disarmament."

In April 1979, the prestigious Templeton Foundation Prize for Progress in Religion was awarded to Founder Niwano in London for his achievement in interreligious cooperation and mutual understanding. In December of that year, Founder Niwano was asked by national senators and religious leaders of the United States to meet Iranian political and religious leaders to persuade them to release the Americans being held hostage by Iranian students in the U.S. embassy in Tehran. He met with the Iranian ambassador in Tokyo and explained his understanding of the issue, expressing the WCRP's hope for a peaceful solution. The following year he received an invitation from the Islamic Republic of Iran to join the International Conference on U.S. Intervention in Iran at Tehran. He met with Iranian Foreign Minister Qotbzadeh, requesting him to affect the prompt release of the hostages.

In July 1981, during the 24th Congress of the IARF, Founder Niwano was elected the 25th president of the IARF and it was decided that the organization would hold its triennial Congress in Japan in 1984, meeting for the first time in Asia. In June 1982, he addressed SSD II on behalf of the IARF. Rissho Kosei-kai had already mounted a nationwide campaign in Japan to collect signatures on a petition calling for disarmament and the abolition of nuclear weapons. The campaign amassed twenty-seven million signatures that were submitted to the UN at SSD II. In September the founder traveled to the Soviet Union at the invitation of the Russian Orthodox church. He visited the Kremlin, where he met with high-ranking Soviet officials to call for the prohibition of first use of nuclear weapons. In 1988 he addressed SSD III at the UN headquarters as the president of Rissho Kosei-kai.

On Nov. 15, 1991, his eldest son, Rev. Nichiko Niwano, succeeded him to become the second president of Rissho Kosei-kai, in the ceremony of the Inheritance of the Lamp of the Dharma. On April 13, 1994, Mrs. Naoko Niwano, who assisted the founder as his wife of 64 years, always holding a firm faith in the Lotus Sutra, died peacefully, with her husband and family at her bedside. On Nov. 3 of that year, Founder Niwano delivered the opening address at the opening session of WCRP VI, held in the Vatican's Synod Hall, as an honorary president of WCRP. Pope John Paul II, who sat beside Founder Niwano at the center of the dais, delivered a commemorative address at the opening session. In March 1998, Rissho Kosei-kai celebrated its sixtieth anniversary at the Great Sacred Hall with the attendance of many of the world's leading religious figures, who were in Japan to participate in a WCRP meeting. In March 1999, his dedication to interreligious cooperation for peace was the source for an autobiographical account published in Japanese under the title of Kono Michi: Ichibutsujo no Sekai o Mezashite (This Way: In Aspiration for the World of the One Buddha Vehicle). Founder Niwano passed away of natural causes in Tokyo on October 4, 1999.