Franz is a member of the 104th Trainees Squad. Franz first appears Ch.3 in walking through Trost District with Eren and Hannah. Eren refers to Hannah and Franz as a couple, which they both embarrassedly deny.

Spoiler

At some point following the breach of the Wall by the Colossal Titan, Franz is attacked by a Titan. He is bitten in half and dies. Armin finds Hannah futilely attempting CPR on what remains of Franz's corpse. He tells her it's useless, and advises her to retreat to the Wall before it's too late.

(Source: Shingeki no Kyojin Wikia)