LSD

LSD is a binary event format used by Atlus in Persona 5. Its purpose is unknown at the moment.

Location
Persona 5's LSDs can be found in the PAC files in data.cpk\event.

EvtTool
EvtTool is a program by TGE that dumps the contents of an EVT, ECS or LSD binary to an editable JSON file, which can be opened with a text editor such as Notepad++. By dragging an LSD onto the EXE, a JSON will be generated (and vice versa). You can download EvtTool here.

Alternatively you can use the program through the commandline by passing in the file path to either an LSD or a JSON file (in case you want to batch the conversion, for example).

P5_LSD.bt
A binary template for 010 Editor can be used to study the structure of an LSD file while hex editing. Download that here.

Format
The format seems to be fairly simple and consists mostly out of a list of lists, with the lists having only a couple of fields, of which only 1 changes throughout files, and contains small entries.

Only one of the fields in the lists seems to ever change from its default value, and its purpose is unknown. It appears to be a number relative to the number of entries in the list.

The entries consist out of 4 bytes and a float value. Their purposes are also unknown.