If you liked Kotaro, I bet you would love the Yuzuki brothers! Similarly, children from those dramas had 'lost' their family at a young age and the drama revolves around the relationships they had formed. This is what I search for a slice of life family dramat but both offers extra cuteness since the main cast are these children who are really great in acting for such a young age. I would often break a tear but the over-all atmosphere of these two dramas is warmth (and cute).