Usagi Drop, Hige wo Soru. Soshite Joshikousei wo Hirou. Recommendations
This recommendation may be premature, since at this writing only three episodes of "Hige wo Soru" have aired and plenty may happen by season end that could give me reason to edit or even recant.
That said, some similarities are already evident. Both revolve around a single guy who lives alone and works a salaried job who with little warning ends up taking a younger girl into his home. In "Usagi Drop" it's a 5-year-old who is technically his aunt despite being 25+ years younger than him. In "Hige wo Soru" it's a 17-year-old runaway, 9 years younger. In both shows his co-workers are supporting characters
Besides the fact UD has a 6 year old rejected girl and not a 17 year old rejected girl, both are pretty similar. Both are light hearted and revolve around the relationship development of the girl and the man. Both have elements of romance but not towards the girls in their care. If you like Usagi Drop, you'll very likely enjoy this.
Both shows present a grown man taking care of a younger girl on trouble and someway against his will. On the process, they overwhelm difficulties and learn to understand and enjoy the company each other.
Both apeal to a grown audience wich can understand the nuances of relationships and the reactions of society to unusual situatons.