I'm not sure I understand the above series of trains. If you change at Keisei-Takasago, what are you changing to? It appears to be the same train. When you get to Oshiage, you have precisely 0 minutes to make the connection? Looking at the map (Apple Maps...) the Keisei line and the Askausa subway line butt up together at Oshiage - it appears one ends and the other starts ... presumably you don't change trains? What does the two-down-arrows symbol at Keisei-Takasago and Oshiage mean? Does it mean you just continue and don't actually change?
The two-down-arrow symbol means your train transitions from one line to another line at that station (eg, from Keisei track to Toei Asakusa track) but you still stay on the same train. Yeah, confusing.
When you go from Yokohama Chinatown to Tokorozawa, for instance, you're on the same train the entire time but your train goes over at least 5 different lines.