Games like DUET
Games like DUET include Florence, Gorogoa, To the Moon, Old Man's Journey, and Machinarium. We matched them by the tags players give DUET on Steam (Casual, Stylized, Faith, Romance, and Hand-drawn): closest matches first, and among equally close ones the better-known games.

Florence
Shared: Casual · Romance · Female Protagonist

Gorogoa
Shared: Hand-drawn · Casual · Stylized

To the Moon
Shared: Story Rich · Romance · Adventure

Old Man's Journey
Shared: Casual · Hand-drawn · Story Rich

Machinarium
Shared: Hand-drawn · Point & Click · Casual

When The Past Was Around
Shared: Female Protagonist · Point & Click · Romance

GRIS
Shared: Female Protagonist · Hand-drawn · Adventure

Before Your Eyes
Shared: Story Rich · Narrative · Emotional

There Is No Game: Wrong Dimension
Shared: Casual · Point & Click · Adventure

Carto
Shared: Hand-drawn · Female Protagonist · Story Rich

Until Then
Shared: Romance · Story Rich · Casual

If Found...
Shared: Casual · Stylized · Female Protagonist

Leila
Shared: Hand-drawn · Casual · Female Protagonist

Storyteller
Shared: Point & Click · Hand-drawn · Casual

Venba
Shared: Casual · Stylized · Female Protagonist

and Roger
Shared: Romance · Point & Click · Interactive Fiction

Once Again
Shared: Casual · Female Protagonist · Adventure

ATRI -My Dear Moments-
Shared: Casual · Romance · Story Rich

Slay the Princess — The Pristine Cut
Shared: Romance · Story Rich · Hand-drawn

Insomnia: Theater in the Head
Shared: Stylized · Hand-drawn · Point & Click

LoveChoice
Shared: Romance · Story Rich · Casual

Mirror 2: Project X
Shared: Female Protagonist · Casual · Interactive Fiction

Room of Depression
Shared: Casual · Story Rich · Adventure

Hidden Folks
Shared: Casual · Hand-drawn · Point & Click