Taiwanese Drama film "Dear Tenant".

For the past five years, Lin Jian-yi, a rooftop tenant, has been looking after his elderly landlord, Zhou Xiu-yu and her grandson, Wang You-yu.
They live together like a family, and it is Lin’s way of remembering Wang Li-wei, the father of You-yu whom he had a relationship with.
But when Mrs. Zhou passes away under suspicious circumstances, her son Wang Li-gang returns from overseas and discovers that the property has been transferred to You-yu, who has been legally adopted by Lin. Li-gang accuses Lin of killing his mother.
He contacts the police with his suspicions.
An autopsy finds narcotics in Zhou’s system at the time of her death, prompting an investigation that reveals a very different side to Lin.
Police recover a deleted gay sex app on Lin’s phone, and one of his hookups turns out to be a drug dealer. Just as he is about to be arrested for murder, Lin takes You-yu and flees deep into the mountains…