Mr. Long (2017)

Both films feature a mother who is suffering from some form of addiction. She is extremely neglectful towards her son and incapable of taking care of him properly.

Both films involve a man falling in love with a prostitute.

Both films show a hitman who forms a special bond with a young kid while trying to start afresh. He can't quite escape from his past, however.

Both productions feature quirky professional killers and the way relationships and people influence them

One film features a Japanese assassin stuck in Taiwan; while the other features a Taiwanese assassin stuck in Japan. Both MLs get involved with a prostitute and land themselves in a situation when they have to care for a little boy

Both has some kind of twisted hero, who goes around hiding and interacting with regular citizens with violence and family content.