When comparing the themes of a writer or filmmaker, it's most fruitful to reference other works by that writer or filmmaker, followed by known influences.
To that end Tony Takitani (Japan, 2004) is a good candidate as it's aanother Murakami adaptation that also deals with loss, sadness and loneliness, allowing for the most meaningful correlation. It's even from the same era (written in 1990, three years after NW).
YourNormally I'd suggest films based on other authors who influenced Murakami, but your description also brings to mind Samaritan Girl (South Korea, 2004) which hits all the notes of suicide, sadness, reflection, contrasting loneliness/isolation and physical intimacy, grappling with adulthood, and the ripple effect of suffering across multiple characters.
However, SG explores these themes in a protracted time and presents the events starkly, leaving emotional analysis to the viewer. This might be a bit too different for your liking. Since it's a Korean film I also worry about seeming to conflate cultures: Murakami has influenced and been influenced by many things, but Korean cinema is not one of them, so making a connection feels like it needs pre-discussion ("not just lumping all of Asia together", etc.). That said, I think it fits the bill.
If you have access to either of the above, give them a try.