With the prevalence of connected TV, streaming is replacing linear TV while expanding its functionality. To structurally explain this replacement based on functional similarity, we applied two-way fixed-effects regression to log data from 197,273 smart TVs in Japan from July 2019 to June 2022. Results showed that professional videos on demand primarily substituted linear TV's recorded viewing, dramas, and movies, whereas substitution by YouTube was broader. Catch-up streaming substituted recorded viewing while complementing viewing without recording. These multiple relationships support the applicability of media substitution theory and foreshadow that functional expansion of streaming would further contribute to linear TV's replacement.