A long alkyl-chained organic molecule, 4,5,6,7-tetrachloro-2-dodecylisoindoline-1,3-dione (1), was crystallized into needle-like crystals in dichloromethane (1DCM) or plate-like ones in tetrahydrofuran (1THF) depending on the recrystallisation solvent. X-ray crystallography analyses revealed the alkyl chains of the molecules, in which they were assembled differently, with the former responding flexibly bendable and elastic deformation, and the later being a permanent plastic one by external mechanical stress. The elastic modulus (E) and hardness (H) indicating both compliant and soft nature, reflecting their weak interaction in crystals, were quantified from the nano-indentation test.