In India, regional nationalism is strongly tied to language. This is particularly the case in the Dravidian-speaking south, especially among speakers of Tamil - Tamil nationalists trot out all manner of absurd claims about the ancientness and purity and divine inspiration of the Tamil language, and about the great power held by the ancient Tamil people (until they were oppressed by the wretched Aryans from the north, of course).
I point this out to provide context for the following question: is there any actual evidence that Tamil (or any other Dravidian language) has a genetic relationship with Japanese?
My cursory reading on the matter has pointed me to Ono Susumu, who appears to have put forth a hypothesis claiming a genetic link - but that was back in the 1980s, and it appears that his hypothesis has been refuted (that said, I'm basing this on secondary writings - I haven't read the actual papers in question). I am unaware of any recent work that bolsters Ono's conclusions.
Yet, Indian news outlets keep on putting out new articles claiming Tamil-Japanese links (e.g. here and here), to the point that many educated Tamil non-linguists take the claims of a Tamil-Japanese genetic relationship as almost-fact. These beliefs are usually of the form "A long, long time ago, the mighty Tamil people traveled through China, crossed into Japan, and brought with them their language, which mixed with or displaced the language already present in Japan at the time" - and you can certainly see how this fits in with the Tamil nationalist narrative I mentioned above.
All that said, I'm left wondering if there's some linguistic (or historical) evidence I'm unaware of that makes claims of a Tamil-Japanese link more plausible.