Mark Kobayashi was a Japanese man whom Grace's parents had arranged for her to marry back East.
Background
He was born and raised back East in Japan. Mark's parents were traditional Japanese.
Grace's parents also being traditional, arranged for him to date their daughter, and wanted her to marry him. Grace thought she might marry him eventually, but not right away.
To Grace's great annoyance, her mother called her regularly to ask her when she would get a serious job, and when she'd accept a date with the 'nice Japanese boy' mom had selected.[1]. He still hadn't been engaged to anyone by the time she traveled to German in 1995.[2] To try to easy things she told her mother to tell him she would be staying in New Orleans for a while longer.
Grace was just still not ready to settle down, and planned to remain working for Gabriel Knight for the time being.[3]
Personality and traits
He was apparently destined for arranged marriage to Grace by her parents. Grace's mom called her regularly asking when she would accept a date to the 'nice Japanese boy" she had selected for her.[4]
See also
Behind the scenes
IT appears that in GK2 hintbook information/novelization that Grace hadn't yet accepted a date with Mark, and he hadn't yet been engaged to anyone.
In GK2 itself, Grace is on the phone with her mom, talking about plans. Before she hangs up she says she tells her mom to tell 'him' (which is apparently a reference to "Mark") that she is going to be in New Orleans for longer, and that she's 'not ready for that yet' this is a reference to dating and marrying Mark Kobiyashi (as confirmed in the hintbook).
In the novelization of GK2 his name is mentioned. However, details are changed, and its mentioned he's gotten engaged, and that Grace missed out. Her mother is highly disappointed in her daughter.
All references to Mark Kobayashi are removed in the 20th Annivesary edition for whatever reason.