In July 1947, preparation were in progress in India for the transfer of power from the British colonial rule. All princely states in India were given a choice to either remain independent, or join either of the states of India or Pakistan. C. P. Ramaswamy Iyer, an efficient ruler, but showing signs of dictatorship, wanted to have Travancore in his clutches. He chose to make Travancore a sovereign kingdom, with full executive powers vested on the Diwan. He declared this intention in his American model constitution. There were oppositions from all quarters. The Diwan chose to suppress the revolts with raw power. On 18 July 1947, Chithira Thirunal Balarama Varma, the King of Travancore, on advise of the Diwan, made the declaration that, Travancore will announce sovereignty on the 26 August.
On 25 July 1947, then 25-year old Mani attacked the Diwan in front of the erstwhile Music Academy (now the Swathi Thirunal College of Music) in Thiruvananthapuram, following a concert in the evening. Ramaswamy Iyer was wounded. Following the incident on 25 July, the King informed the Viceroy the decision to join the Union of India. On 19 August 1947, C. P. Ramaswamy Iyer formally resigned as Diwan.
After the independence, Mani served as a member of the local panchayat for more than a decade. He also contested to the Kerala Legislative Assembly from the Kuttanad constituency in 1965, as an independent candidate (not the nominee of any political party, But RSP leaders have instructed him to submit the nomination, So he can be considered as an RSP Candidate), but without success.
Mani married Lalithammal from Senkottai in 1963 at the Subrahmanya Temple in Valliyur. He was then 41 years old, 18 years older than his wife (who was born in 1940). The proposal was introduced by Mani's sister Lakshmi, who was married from Senkottai. Lakshmi knew Lalitha's father Venkatarama Iyer, who was a motor company mechanic very well. According to Lalitha, she was taken by Lakshmi to Konattu Madom in Ambalappuzha, and at that time, Mani was no there. Some time later, Lakshmi told Lalitha to clean her face and feet in the pond on the southern side. After coming back to the Madom, everyone went to Ambalapuzha Sri Krishna Temple, and while going, she met her future husband speaking to a stranger in an Ayurvedic pharmacy. Two weeks later, their marriage was conducted. Mani's hair had already been grey, and his teeth were removed after a serious disease at the age of 30. Mani and Lalitha did not have children.
Mani felt alienated by the party as well as the state in the later years of his life. He spent his last days abandoned and struggling with diseases. When he suffered from loneliness, he found a solace in devotion. It is also said that the feeling of guilt affected him deeply. During some nights, after Ambalapuzha temple was closed, he conducted 'sayana pradakshinam' around the temple. Sometimes, he went to Sabarimala without informing anyone. Finally, Mani died on September 20, 1987, at an age of 65, in the Chest Diseases Hospital, Pulayanarkotta, Thiruvananthapuram. He was cremated in his home premises on the next day. His brother-in-law conducted the rituals. The place where he was cremated is now part of railway line. His wife Lalitha outlived him for 30 years, finally dying on June 14, 2017 aged 77.
Refer the Biography Sir C. P.ye vadhikan sramicha K. C. S. Mani by Yedukula Kumar G. 1997, published by DC Books - for more details.T. Sivasubramania Iyer, played by Mohanlal in Rakthasakshikal Sindabad (1998).