Krishnan quits his job in Bombay and decides to stay in Madras to take care of his ailing mother.

In the meantime Krishnan is elected as the union leader, defeating the office staff candidate supported by Shanthi Devi.

Shanthi Devi changes a policy in her company which agitates all the workers and they go on an indefinite hunger strike, which is headed by Krishnan.

Shanthi Devi is angered by this move and begins destroying her house, humiliated at having lost to Krishnan.

Krishnan's mother learns of their bitter relationship and, despite recovering from paralysis, immediately dies of guilt.

An assassination attempt is made on Shanthi Devi by her business rival Sathish, but Krishnan kills him and saves her and ultimately she realises her mistake.

Mannan is a remake of the 1986 Kannada film Anuraga Aralithu,[3] which in turn was based on the novel Anuragada Anthapura by H. G.

[13] Writing for PopMatters, Kumuthan Maderya said, "At the heart of Mannan is the conceit that domestic violence, physical and emotional, is a civil war of attrition that inevitably hemorrhages both parties".

[15][16] Rajinikanth made his debut in playback singing with this film,[17] through the song "Adikkuthu Kuliru".

[21] The same song was sung by Tamil Nadu governor R. N. Ravi in a Mother's Day function celebration in 2023.

[23][24] Sundarji of Kalki felt the story and visuals were not fit for Rajinikanth, and Vijayashanti's rage was a negative, bringing her performance down a certain amount.