Taru adjective, Adverb taking the 'to' particle
uninterested; unconcerned; indifferent; dispassionate; matter-of-fact; detached
彼は他人の苦しみに対して淡淡だ。He is indifferent to the suffering of others. plain; light; simple; bland
flowing gently
Also written 淡淡【たんたん】、澹々【たんたん】、澹澹【たんたん】