Responses
I think starting this page, he tian is appoarching Jian Yi
http://www.mangago.zone/read-manga/19_days/bt/c102/pg-8/
In a few chapter we get his name
http://www.mangago.zone/read-manga/19_days/bt/c104/pg-2/
When Mo Guan went to fight with Jian Yi is when He Tian and Mo Guan first meet
http://www.mangago.zone/read-manga/19_days/bt/c125/pg-6/
The next day or possible a few days after the fight He Tian leaves his apartment to grab some food, he mets Mo Guan on the street and they start their "interesting" relationship.
http://www.mangago.zone/read-manga/19_days/bt/c130/pg-3/
HE TIAN DOES ANYONE KNOW WHEN DID HE FIRST APPEARED? AND ALSO WHEN HE FIRST MET MO GUANSHAN