Kore wa Okaa-san no Koi no Hanashi: Gokudou Wakashu to Jire Kyun Doukyo

After losing her husband in a traffic accident, Kaho runs a coffee shop and raises her only daughter, Suzu, on her own. Ever since she was a child, Kaho has had a hard time laughing, and is clearly not suited to working in the hospitality industry. Two years later, the coffee shop is in dire straits, and she's in danger of not even being able to pay her utility bills. Then, a handsome man who seems like a savior appears before Kaho. His name is "Matsuoka-san from the Hanatora-gumi"...!? A pure love story between a single mother and a gangster living under the same roof!

(Source: Kodansha, translated)