Boku dake ga Inai Machi, 3-gatsu no Lion Recommendations
Both shows have a number of important similarities despite having opposite and completely different themes with Sangatsu being more light-hearted compared to BokuMachi's serious content.
The male protagonists wear eye-glasses and tend to be silent or serious.
They have their own dark and trouble pasts that often keeps on haunting them and they have to face them before moving on.
They have friends who are ready to support them when they are sad and troubled.
Aside from characters, there is also symbolism portrayed on both shows.
If you like Sangatsu No Lion but want a more serious twist, then I recommend watching BokuMachi.